Skip to main content

Full text of "The riddle of the universe at the close of the nineteenth century"

See other formats






Thomas 17. Hunt ing t on, jr 






(Ph.D., M.D., LL.D., Sc.D., and Professor at the 
University of Jena) 





Copyright, 1900, by HARPER & BROTHERS. 
All rights reserved. 
































INDEX 385 


THE present study of the monistic philosophy is 
intended for thoughtful readers of every condi- 
tion who are united in an honest search for the truth. 
An intensification of this effort of man to attain a 
knowledge of the truth is one of the most salient 
features of the nineteenth century. That is easily ex- 
plained, in the first place, by the immense progress 
of science, especially in its most important branch, 
the history of humanity ; it is due, in the second place, 
to the open contradiction that has developed during 
the century between science and the traditional " Rev- 
elation " ; and, finally, it arises from the inevitable ex- 
tension and deepening of the rational demand for an 
elucidation of the innumerable facts that have been 
recently brought to light, and for a fuller knowledge 
of their causes. 

Unfortunately, this vast progress of empirical knowl- 
edge in our " Century of Science " has not been ac- 
companied by a corresponding advancement of its 
theoretical interpretation that higher knowledge of 
the causal nexus of individual phenomena which we 
call philosophy. We find, on the contrary, that the 
abstract and almost wholly metaphysical science 
which has been taught in our universities for the 


last hundred years under the name of "philosophy" 
is far from assimilating our hard-earned treasures of 
experimental research. On the other hand, we have 
to admit, with equal regret, that most of the repre- 
sentatives of what is called "exact science'* are con- 
tent with the special care of their own narrow branches 
of observation and experiment, and deem superfluous 
the deeper study of the universal connection of the 
phenomena they observe that is, philosophy. While 
these pure empiricists "do not see the wood for the 
trees/' the metaphysicians, on the other hand, are satis- 
fied with the mere picture of the wood, and trouble not 
about its individual trees. The idea of a "philosophy 
of nature," to which both those methods of research, 
the empirical and the speculative, naturally converge, 
is even yet contemptuously rejected by large numbers 
of representatives of both tendencies. 

This unnatural and fatal opposition between science 
and philosophy, between the results of experience and 
of thought, is undoubtedly becoming more and more 
onerous and painful to thoughtful people. That is 
easily proved by the increasing spread of the immense 
popular literature of "natural philosophy" which has 
sprung up in the course of the last half-century. It is 
seen, too, in the welcome fact that, in spite of the 
mutual aversion of the scientific observer and the 
speculative philosopher, nevertheless eminent thinkers 
from both camps league themselves in a united ef- 
fort to attain the solution of that highest object of in- 
quiry which we briefly denominate the "world-riddles." 
The studies of these " world - riddles " which I offer 
in the present work cannot reasonably claim to give 
a perfect solution of them; they merely offer to a 
wide circle of readers a critical inquiry into the prob- 



lem, and seek to answer the question as to how nearly 
we have approached that solution at the present day. 
What stage in the attainment of truth have we actually 
arrived at in this closing year of the nineteenth cen- 
tury? What progress have we really made during its 
course towards that immeasurably distant goal ? 

The answer which I give to these great questions 
must, naturally, be merely subjective and only partly 
correct; for my knowledge of nature and my ability 
to interpret its objective reality are limited, as are 
those of every man. The one point that I can claim 
for it, and which, indeed, I must ask of my strongest 
opponents, is that my Monistic Philosophy is sincere 
from beginning to end it is the complete expression 
of the conviction that has come to me, after many 
years of ardent research into Nature and unceasing 
reflection, as to the true basis of its phenomena. For 
fully half a century has my mind's work proceeded, 
and I now, in my sixty-sixth year, may venture to 
claim that it is mature ; I am fully convinced that this 
"ripe fruit" of the tree of knowledge will receive no 
important addition and suffer no substantial modifi- 
cation during the brief spell of life that remains to me. 

I presented all the essential and distinctive elements 
of my monistic and genetic philosophy thirty-three 
years ago, in my General Morphology of Organisms, a 
large and laborious work, which has had but a limited 
circulation. It was the first attempt to apply in detail 
the newly established theory of evolution to the whole 
science of organic forms. In order to secure the accept- 
ance of at least one part of the new thought which it 
contained, and to kindle a wider interest in the greatest 
advancement of knowledge that our century has wit- 
nessed, I published my Natural History of Creation 



two years afterwards. As this less complicated work, 
in spite of its great defects, ran into nine large editions 
and twelve different translations, it has contributed 
not a little to the spread of monistic views. The same 
may be said of the less known Anthropogeny* (1874), 
in which I set myself the difficult task of rendering the 
most important facts of the theory of man's descent 
accessible and intelligible to the general reader; the 
fourth, enlarged, edition of that work appeared in 
1891. In the paper which I read at the fourth Inter- 
national Congress of Zoology at Cambridge, in 1898, 
on " Our Present Knowledge of the Descent of Man " t 
(a seventh edition of which appeared in 1899), I treated 
certain significant and particularly valuable advances 
which this important branch of anthropology has re- 
cently made. Other isolated questions of our modern 
natural philosophy, which are peculiarly interesting, 
have been dealt with in my Collected Popular Lectures 
on the Subject of Evolution (1878). Finally, I have 
briefly presented the broad principles of my monistic 
philosophy and its relation to the dominant faith in 
my Confession of Faith of a Man of Science : Monism 
as a Connecting Link between Religion and Science J 
(1892, eighth edition, 1899). 

The present work on The Riddle of the Universe 
is the continuation, confirmation, and integration of 
the views which I have urged for a generation in the 
aforesaid volumes. It marks the close of my studies 
on the monistic conception of the universe. The earlier 

* There are two English translations, The Evolution of Man 
(1879) and The Pedigree of Man (1880). 

t The English translation, by Dr. Hans Gadow, bears the title 
of The Last Link. 

J English translation, by J. Gilchrist, with the title of Monism. 



plan, which I projected many years ago, of construct- 
ing a complete "System of Monistic Philosophy" on 
the basis of evolution will never be carried into effect 
now. My strength is no longer equal to the task, 
and many warnings of approaching age urge me to 
desist. Indeed, I am wholly a child of the nineteenth 
century, and with its close I draw the line under my 
life's work. 

The vast extension of human knowledge which has 
taken place during the present century, owing to a 
happy division of labor, makes it impossible to-day 
to range over all its branches with equal thorough- 
ness, and to show their essential unity and connec- 
tion. Even a genius of the highest type, having an 
equal command of every branch of science, and largely 
endowed with the artistic faculty of comprehensive 
presentation, would be incapable of setting forth a 
complete view of the cosmos in the space of a moderate 
volume. My own command of the various branches of 
science is uneven and defective, so that I can attempt 
no more than to sketch the general plan of such a 
world-picture, and point out the pervading unity of its 
parts, however imperfect be the execution. Thus it 
is that this work on the world-enigma has something 
of the character of a sketch-book, in which studies of 
unequal value are associated. As the material of the 
book was partly written many years ago, and partly 
produced for the first time during the last few years, 
the composition is, unfortunately, uneven at times; 
repetitions, too, have proved unavoidable. I trust those 
defects will be overlooked. 

In taking leave of my readers, I venture the hope 
that, through my sincere and conscientious work in 
spite of its faults, of which I am not unconscious 



I have contributed a little towards the solution of the 
great enigma. Amid the clash of theories, I trust 
that I have indicated to many a reader who is absorbed 
in the zealous pursuit of purely rational knowledge 
that path which, it is my firm conviction, alone leads 
to the truth the path of empirical investigation and 
of the Monistic Philosophy which is based upon it. 



HTHE hour is close upon us when we shall commence 
our retrospect of one of the most wonderful sec- 
tions of time that was ever measured by the sweep 
of the earth. Already the expert is at work, dissect- 
ing out and studying his particular phase of that vast 
world of thought and action we call the nineteenth 
century. Art, literature, commerce, industry, politics, 
ethics all have their high interpreters among us; 
but in the chance of life it has fallen out that there is 
none to read aright for us, in historic retrospect, what 
after ages will probably regard as the most salient 
feature of the nineteenth century the conflict of the- 
ology with philosophy and science. The pens of our 
Huxleys, and Tyndalls, and Darwins lie where they 
fell; there is none left in strength among us to sum 
up the issues of that struggle with knowledge and 

In these circumstances it has been thought fitting 
that we should introduce to English readers the latest 
work of Professor Haeckel. Germany, as the reader 
will quickly perceive, is witnessing the same strange 
reaction of thought that we see about us here in Eng- 
land, yet Die Weltrdthsel found an immediate and very 
extensive circle of readers. One of the most prominent 



zoologists of the century, Professor Haeckel, has a 
unique claim to pronounce with authority, from the 
scientific side, on what is known as "the conflict of 
science and religion." In the contradictory estimates 
that are urged on us for the modern ecclesiastic is 
as emphatic in his assurance that the conflict has 
ended favorably to theology as the rationalist is with 
'his counter-assertion the last words of one of the 
leading combatants of the second half of the century, 
still, happily, in full vigor of mind, will be heard with 
respect and close attention. 

A glance at the index of the work suffices to indicate 
its comprehensive character. The judgment of the dis- 
tinguished scientist cannot fail to have weight on all 
the topics included ; yet the reader will soon discover 
a vein of exceptionally interesting thought in the chap- 
ters on evolution. The evolution of the human body 
is no longer a matter of serious dispute. It has passed 
the first two tribunals those of theology and of an & 
priori philosophy and is only challenged at the third 
and last that of empirical proof by the decorative 
heads of scientific bodies and a few isolated thinkers. 

"Apparent rari nantes in gurgite vasto." 

But the question of the evolution of the human mind, 
or soul, has been successfully divorced from that of 
the body. Roman Catholic advanced theologians, 
whose precise terminology demanded a clear position, 
admit the latter and deny the former categorically. 
Other theologians, and many philosophers, have still 
a vague notion that the evidence for the one does not 
impair their sentimental objection to the other. Dr. 
HaeckeFs work summarizes the evidence for the evo- 



lution of mind in a masterly and profoundly interesting 
fashion. It seems impossible to follow his broad sur- 
vey of the psychic world, from protist to man, without 
bearing away a conviction of the natural origin of 
every power and content of the human soul. 


October, 1900. 



The Condition of Civilization and of Thought at the Close of the 
Nineteenth Century Progress of Our Knowledge of Nature, 
of the Organic and Inorganic Sciences The Law of Substance 
and the Law of Evolution Progress of Technical Science 
and of Applied Chemistry Stagnancy in other Departments 
of Life : Legal and Political Administration, Education, and 
the Church Conflict of Reason and Dogma Anthropism 
Cosmological Perspective Cosmological Theorems Refuta- 
tion of the Delusion of Man's Importance Number of " World- 
Riddles "Criticism of the " Seven " Enigmas The Way to 
Solve Them Function of the Senses and of the Brain In- 
duction and Deduction Reason, Sentiment, and Revelation 
Philosophy and Science Experience and Speculation 
Dualism and Monism 

HP HE close of the nineteenth century offers one of the 
most remarkable spectacles to the thoughtful ob- 
server. All educated people are agreed that it has in 
many respects immeasurably outstripped its predeces- 
sors, and has achieved tasks that were deemed impracti- 
cable at its commencement. An entirely new character 
has been given to the whole of our modern civilization, 
not only by our astounding theoretical progress in sound 
knowledge of nature, but also by the remarkably fertile 


practical application of that knowledge in technical 
science, industry, commerce, and so forth. On the 
other hand, however, we have made little or no prog- 
ress in moral and social life, in comparison with earlier 
centuries; at times there has been serious reaction. 
And from this obvious conflict there have arisen, not 
only an uneasy sense of dismemberment and falseness, 
but even the danger of grave catastrophes in the polit- 
ical and social world. It is, then, not merely the right, 
but the sacred duty, of every honorable and humani- 
tarian thinker to devote himself conscientiously to the 
settlement of that conflict, and to warding off the dan- 
gers that it brings in its train. In our conviction this 
can only be done by a courageous effort to attain the 
truth, and by the formation of a clear view of the world 
a view that shall be based on truth and conformity 
to reality. 

If we recall to mind the imperfect condition of science 
at the beginning of the century, and compare this with 
the magnificent structure of its closing years, we are 
compelled to admit that marvellous progress has been 
made during its course. Every single branch of science 
can boast that it has, especially during the latter half 
of the century, made numerous acquisitions of the ut- 
most value. Both in our microscopic knowledge of the 
i little and in our telescopic investigation of the great 
we have attained an invaluable insight that seemed in- 
conceivable a hundred years ago. Improved methods of 
microscopic and biological research have not only re- 
vealed to us an invisible world of living things in the 
kingdom of the protists, full of an infinite wealth of 
forms, but they have taught us to recognize in the tiny 
cell the all-pervading * elementary organism " of whose 
social communities the tissues the body of every 


multicellular plant and animal, even that of man, is 
composed. This anatomical knowledge is of extreme 
importance; and it is supplemented by the embryo- 
logical discovery that each of the higher multicellular 
organisms is developed out of one simple cell, the im- 
pregnated ovum. The u cellular theory," which has 
been founded on that discovery, has given us the first 
true interpretation of the physical, chemical, and even 
the psychological processes of life those mysterious 
phenomena for whose explanation it had been custom- 
ary to postulate a supernatural " vital force " or " im- 
mortal soul." Moreover, the true character of disease 
has been made clear and intelligible to the physician 
for the first time by the cognate science of Cellular 

The discoveries of the nineteenth century in the in- 
organic world are no less important. Physics has made 
astounding progress in every section of its province 
in optics and acoustics, in magnetism and electricity, 
in mechanics and thermo-dynamics ; and, what is still 
more important, it has proved the unity of the forces 
of the entire universe. The mechanical theory of heat 
has shown how intimately they are connected, and how 
each can, in certain conditions, transform itself directly 
into another. Spectral analysis has taught us that the 
same matter which enters into the composition of all 
bodies on earth, including its living inhabitants, builds 
up the rest of the planets, the sun, and the most distant 
stars. Astro-physics has considerably enlarged our 
cosmic perspective in revealing to us, in the immeasur- 
able depths of space, millions of circling spheres larger 
than our earth, and, like it, in endless transformation, 
in an eternal rhythm of life and death. Chemistry has 
introduced us to a multitude of new substances, all of 



which arise from the combination of a few (about sev- 
enty) elements that are incapable of further analysis ; 
some of them play a most important part in every branch 
of life. It has been shown that one of these elements 
carbon is the remarkable substance that effects the 
endless variety of organic syntheses, and thus may be 
considered " the chemical basis of life." All the par- 
ticular advances, however, of physics and chemistry 
yield in theoretical importance to the discovery of the 
great law which brings them all to one common focus, 
the " Law of Substance." As this fundamental cosmic 
law establishes the eternal persistence of matter and 
force, their unvarying constancy throughout the entire 
universe, it has become the pole-star that guides our 
Monistic Philosophy through the mighty labyrinth to 
a solution of the world-problem. 

Since we intend to make a general survey of the act- 
ual condition of our knowledge of nature and its prog- 
ress during the present century in the following chap- 
ters, we shall delay no longer with the review of its 
particular branches. We would only mention one im- 
portant advance, which was contemporary with the dis- 
covery of the law of substance, and which supplements 
it the establishment of the theory of evolution. It is 
true that there were philosophers who spoke of the evo- 
lution of things a thousand years ago ; but the recogni- 
tion that such a law dominates the entire universe, and 
that the world is nothing else than an eternal " evolution 
of substance," is a fruit of the nineteenth century. It 
was not until the second half of this century that it at- 
tained to perfect clearness and a universal application. 
The immortal merit of establishing the doctrine on an 
empirical basis, and pointing out its world-wide appli- 
cation, belongs to the great scientist Charles Darwin; 



he it was who, in 1859, supplied a solid foundation foi 
the theory of descent, which the able French naturalist 
Jean Lamarck had already sketched in its broad out- 
lines in 1809, and the fundamental idea of which had 
been almost prophetically enunciated in 1799 by Ger- 
many's greatest poet and thinker, Wolfgang Goethe. 
In that theory we have the key to " the question of all 
questions, " to the great enigma of " the place of man in 
nature," and of his natural development. If we are in 
a position to-day to recognize the sovereignty of the 
law of evolution and, indeed, of a monistic evolution 
in every province of nature, and to use it, in conjunc- 
tion with the law of substance, for a simple interpreta- 
tion of all natural phenomena, we owe it chiefly to those 
three distinguished naturalists; they shine as three 
stars of the first magnitude amid all the great men of 
the century. 

This marvellous progress in a theoretical knowledge 
of nature has been followed by a manifold practical ap- 
plication in every branch of civilized life. If we are to- 
day in the " age of commerce," if international trade 
and communication have attained dimensions beyond 
the conception of any previous age, if we have tran- 
scended the limits of space and time by our telegraph 
and telephone, we owe it, in the first place, to the tech- 
nical advancement of physics, especially in the appli- 
cation of steam and electricity. If, in photography, 
we can, with the utmost ease, compel the sunbeam to 
create for us in a moment's time a correct picture of 
any object we like ; if we have made enormous progress 
in agriculture, and in a variety of other pursuits ; if, in 
surgery, we have brought an infinite relief to human 
pain by our chloroform and morphia, our antiseptics 
and serous therapeutics, we owe it all to applied chem- 



istry. But it is so well known how much we have sur- 
passed all earlier centuries through these and other sci- 
entific discoveries that we need linger over the question 
no longer. 

While we look back with a just pride on the immense 
progress of the nineteenth century in a knowledge of 
nature and in its practical application, we find, unfortu- 
nately, a very different and far from agreeable picture 
when we turn to another and not <Hss important prov- 
ince of modern life. To our great regret we must en- 
dorse the words of Alfred Wallace: "Compared with 
our astounding progress in physical science and its 
practical application, our system of government, of ad- 
ministrative justice, and of national education, and our 
entire social and moral organization, remain in a state 
of barbarism." To convince ourselves of the truth of 
this grave indictment we need only cast an unprejudiced 
glance at our public life, or look into the mirror that is 
daily offered to us by the press, the organ of public sen- 

We begin our review with justice, the fundamentum 
regnorum. No one can maintain that its condition to- 
day is in harmony with our advanced knowledge of 
man and the world. Not a week passes in which we 
do not read of judicial decisions over which every 
thoughtful man shakes his head in despair; many of 
the decisions of our higher and lower courts are simply 
unintelligible. We are not referring in the treatment 
of this particular " world-problem " to the fact that 
many modern states, in spite of their paper constitu- 
tions, are really governed with absolute despotism, and 
that many who occupy the bench give judgment less 
in accordance with their sincere conviction than with 
wishes expressed in higher quarters. We readily ad- 



mit that the majority of judges and counsel decide con* 
scientiously, and err simply from human frailty. Most 
of their errors, indeed, are due to defective preparation. 
It is popularly supposed that these are just the men of 
highest education, and that on that very account they 
have the preference in nominations to different offices. 
However, this famed " legal education " is for the most 
part rather of a formal and technical character. They 
have but a superficlB acquaintance with that chief and 
peculiar object of their activity, the human organism, 
and its most important function, the mind. That is ev- 
ident from the curious views as to the liberty of the will, 
responsibility, etc., which we encounter daily. I once 
told an eminent jurist that the tiny spherical ovum from 
w r hich every man is developed is as truly endowed with 
life as the embryo of two, or seven, or even nine months ; 
he laughed incredulously. Most of the students of ju- 
risprudence have no acquaintance with anthropology, 
psychology, and the doctrine of evolution the very 
first requisites for a correct estimate of human nature. 
They have " no time " for it ; their time is already too 
largely bespoken for an exhaustive study of beer and 
wine and for the noble art of fencing. The rest of their 
valuable study-time is required for the purpose of learn- 
ing some hundreds of paragraphs of law books, a 
knowledge of which is supposed to qualify the jurist 
for any position whatever in our modern civilized com- 

We shall touch but lightly on the unfortunate prov- 
ince of politics, for the unsatisfactory condition of the 
modern political world is only too familiar. In a great 
measure its evils are due to the fact that most of our 
officials are jurists that is, men of high technical edu- 
cation, but utterly devoid of that thorough knowledge 



of human nature which is only obtained by the study 
of comparative anthropology and the monistic psychol- 
ogy men without an acquaintance with those social 
relations of which we find the earlier types in compara- 
tive zoology and the theory of evolution, in the cellular 
theory, and the study of the protists. We can only ar- 
rive at a correct knowledge of the structure and life of 
the social body, the state, through a scientific knowl- 
edge of the structure and life of the individuals who 
compose it, and the cells of which they are in turn com- 
posed. If our political rulers and our " representatives 
of the people " possessed this invaluable biological and 
anthropological knowledge, we should not find our 
journals so full of the sociological blunders and political 
nonsense which at present are far from adorning our 
parliamentary reports, and even many of our official 
documents. Worst of all is it when the modern state 
flings itself into the arms of the reactionary Church, 
and when the narrow-minded self-interest of parties 
and the infatuation of short-sighted party-leaders lend 
their support to the hierarchy. Then are witnessed 
such sad scenes as the German Reichstag puts before 
our eyes even at the close of the nineteenth century. We 
have the spectacle of the educated German people in 
the power of the ultramontane Centre, under the rule 
of the Roman papacy, which is its bitterest and most 
dangerous enemy. Then superstition and stupidity 
reign instead of right and reason. Never will our gov- 
ernment improve until it casts off the fetters of the 
Church and raises the views of the citizens on man and 
the world to a higher level by a general scientific edu- 
cation. That does not raise the question of any special 
form of constitution. Whether a monarchy or a re- 
public be preferable, whether the constitution should be 



aristocratic or democratic, are subordinate questions in 
comparison with the supreme question : Shall the mod- 
ern civilized state be spiritual or secular ? Shall it be 
theocratic ruled by the irrational formulae of faith and 
by clerical despotism or nomocratic under the sov- 
ereignty of rational laws and civic right? The first 
task is to kindle a rational interest in our youth, and to 
uplift our citizens and free them from superstition. That 
can only be achieved by a timely reform of our schools. 
Our education of the young is no more in harmony 
with modern scientific progress than our legal and polit- 
ical world. Physical science, which is so much more 
important than all other sciences, and which, properly 
understood, really embraces all the so-called moral 
sciences, is still regarded as a mere accessory in our 
schools, if not treated as the Cinderella of the curricu- 
lum. Most of our teachers still give the most prom- 
inent place to that dead learning which has come down 
from the cloistral schools of the Middle Ages. In the 
front rank we have grammatical gymnastics and an 
immense waste of time over a " thorough knowledge " 
of classics and of the history of foreign nations. Ethics, 
the most important object of practical philosophy, is 
entirely neglected, and its place is usurped by the eccle- 
siastical creed. Faith must take precedence over knowl- 
edge not that scientific faith which leads to a monistic 
religion, but the irrational superstition that lays the 
foundation of a perverted Christianity. The valuable 
teaching of modern cosmology and anthropology, of 
biology and evolution, is most inadequately imparted, 
if not entirely unknown, in our higher schools ; while 
the memory is burdened with a mass of philological 
and historical facts which are utterly useless, either 
from the point of view of theoretical education or for 



the practical purposes of life. Moreover, the antiquated 
arrangements and the distribution of faculties in the 
universities are just as little in harmony with the point 
we have reached in monistic science as the curriculum 
of the primary and secondary schools. 

The climax of the opposition to modern education and 
its foundation, advanced natural philosophy, is reached, 
of course, in the Church. We are not speaking here of 
ultramontane papistry, nor of the orthodox evangel- 
ical tendencies, which do not fall far short of it in igno- 
rance and in the crass superstition of their dogmas. We 
are imagining ourselves for the moment to be in the 
church of a liberal Protestant minister, who has a good 
average education, and who finds room for " the rights 
of reason " by the side of his faith. There, besides ex- 
cellent moral teaching, which is in perfect harmony with 
our own monistic ethics, and humanitarian discussion 
of which we cordially approve, we hear ideas on the 
nature of God, of the world, of man, and of life which 
are directly opposed to all scientific experience. It is 
no wonder that physicists and chemists, doctors and 
philosophers, who have made a thorough study of nat- 
ure, refuse a hearing to such preachers. Our theo- 
logians and our politicians are just as ignorant as our 
philosophers and our jurists of that elementary knowl- 
edge of nature which is based on the monistic theory of 
evolution, and which is already far exceeded in the tri- 
umph of our modern learning. 

From this opposition, which we can only briefly point 
out at present, there arise grave conflicts in our modern 
life which urgently demand a settlement. Our modern 
education, the outcome of our great advance in knowl- 
edge, has a claim upon every department of public and 
private life; it would see humanity raised, by the in- 



strumentality of reason, to that higher grade of culture, 
and, consequently, to that better path towards happi- 
ness which has been opened out to us by the progress 
of modern science. That aim, however, is vigorously 
opposed by the influential parties who would detain the 
mind in trie exploded views of the Middle Ages with re- 
gard to the most important problems of life ; they linger 
in the fold of traditional dogma, and would have reason 
prostrate itself before their " higher revelation." That 
is the condition of things, to a very large extent, in the- 
ology and philosophy, in sociology and jurisprudence. 
It is not that the motives of the latter are to be attributed, 
as a rule, to pure self-interest ; they spring partly from 
ignorance of the facts, and partly from an indolent ac- 
quiescence in tradition. The most dangerous of the 
three great enemies of reason and knowledge is not 
malice, but ignorance, or, perhaps, indolence. The 
gods themselves still strive in vain against these two 
latter influences when they have happily vanquished 
the first. 

One of the main supports of that reactionary system 
is still what we may call " anthropism." I designate by 
this term " that powerful and world-wide group of erro- 
neous opinions which opposes the human organism to 
the whole of the rest of nature, and represents it to be 
the preordained end of the organic creation, an entity 
essentially distinct from it, a godlike being." Closer 
examination of this group of ideas shows it to be made 
up of three different dogmas, which we may distinguish 
as the anthropocentric, the anthropomorphic, and the 

I. The anthropocentric dogma culminates in the idea 

*E. Haeckel, S ystematische Phylogenie, 1895, vol. iii., pp. 646-50. 
(Anthropolatry means * A divine worship of human nature.") 



that man is the preordained centre and aim of all ter- 
restrial life or, in a wider sense, of the whole universe. 
As this error is extremely conducive to man's interest, 
and as it is intimately connected with the creation-myth 
of the three great Mediterranean religions, and with the 
dogmas of the Mosaic, Christian, and Mohammedan 
theologies, it still dominates the greater part of the civ- 
ilized world. 

II. The anthropomorphic dogma is likewise connected 
with the creation-myth of the three aforesaid religions, 
and of many others. It likens the creation and control 
of the world by God to the artificial creation of a tal- 
ented engineer or mechanic, and to the administration 
of a wise ruler. God, as creator, sustainer, and ruler 
of the world, is thus represented after a purely human 
fashion in his thought and work. Hence it follows, in 
turn, that man is godlike. * God made- man to His 
own image and likeness. " The older, naive mythology 
is pure " homotheism," attributing human shape, flesh, 
and blood to the gods. It is more intelligible than the 
modern mystic theosophy that adores a personal God 
as an invisible properly speaking, gaseous being, 
yet makes him think, speak, and act in human fashion ; 
it gives us the paradoxical picture of a " gaseous verte- 

III. The anthropolatric dogma naturally results from 
this comparison of the activity of God and man ; it ends 
in the apotheosis of the human organism. A further 
result is the belief in the personal immortality of the 
soul, and the dualistic dogma of the twofold nature of 
man, whose "immortal soul" is conceived as but the 
temporary inhabitant of the mortal frame. Thus these 
three anthropistic dogmas, variously adapted to the re- 
spective professions of the different religions, came at 



length to be vested with an extraordinary importance, 
and proved the source of the most dangerous errors. 
The anthropistic view of the world which springs from 
them is in irreconcilable opposition to our monistic sys- 
tem ; indeed, it is at once disproved by our new cosmo- 
logical perspective. 

Not only the three anthropistic dogmas, but many 
other notions of the dualistic philosophy and orthodox 
religion, are found to be untenable as soon as we regard 
them critically from the cosmological perspective of our 
monistic system. We understand by that the compre- 
hensive view of the universe which we have from the 
highest point of our monistic interpretation of nature. 
From that stand-point we see the truth of the following 
"cosmological theorems/' most of which, in our opin- 
ion, have already been amply demonstrated : 

(i) The universe, or the cosmos, is eternal, infinite, 
and illimitable. (2) Its substance, with its two attri- 
butes (matter and energy), fills infinite space, and is in 
eternal motion. (3) This motion runs on through in- 
finite time as an unbroken development, with a peri- 
odic change from life to death, from evolution to devo- 
lution. (4) The innumerable bodies which are scat- 
tered about the space-filling ether all obey the same 
" law of substance;" while the rotating masses slowly 
move towards their destruction and dissolution in one 
part of space others are springing into new life and 
development in other quarters of the universe. (5) Our 
sun is one of these unnumbered perishable bodies, and 
our earth is one of the countless transitory planets that 
encircle them. (6) Our earth has gone through a long 
process of cooling before water, in liquid form (the first 
condition of organic life), could settle thereon. (7) The 
ensuing biogenetic process, the slow development and 



transformation of countless organic forms, must have 
taken many millions of years considerably over a hun- 
dred.* (8) Among the different kinds of animals which 
arose in the later stages of the biogenetic process on 
earth the vertebrates have far outstripped all other com- 
petitors in the evolutionary race. (9) The most impor- 
tant branch of the vertebrates, the mammals, were de- 
veloped later (during the triassic period) from the lower 
amphibia and the reptilia. (10) The most perfect and 
most highly developed branch of the class mammalia 
is the order of primates, which first put in an appear- 
ance, by development from the lowest prochoriata, at 
the beginning of the Tertiary period at least three mill- 
ion years ago. (n) The youngest and most perfect 
twig of the branch primates is man, who sprang from 
a series of manlike apes towards the end of the Tertiary 
period. (12) Consequently, the so-called history of the 
world " that is, the brief period of a few thousand 
years which measures the duration of civilization is 
an evanescently short episode in the long course of or- 
ganic evolution, just as this, in turn, is merely a small 
portion of the history of our planetary system ; and as 
our mother-earth is a mere speck in the sunbeam in the 
illimitable universe, so man himself is but a tiny grain 
of protoplasm in the perishable framework of organic 

Nothing seems to me better adapted than this mag- 
nificent cosmological perspective to give us the proper 
standard and the broad outlook which we need in the 
solution of the vast enigmas that surround us. It not 
only clearly indicates the true place of man in nature, 
but it dissipates the prevalent illusion of man's supreme 

* Cf . my Cambridge lecture, The Last Link, " Geological Time 
and Evolution." 


importance, and the arrogance with which he sets him- 
self apart from the illimitable universe, and exalts him- 
self to the position of its most valuable element. This 
boundless presumption of conceited man has misled 
him into making himself " the image of God," claiming 
an " eternal life " for his ephemeral personality, and 
imagining that he possesses unlimited "freedom of 
will." The ridiculous imperial folly of Caligula is but 
a special form of man's arrogant assumption of divin- 
ity. Only when we have abandoned this untenable 
illusion, and taken up the correct cosmological perspec- 
tive, can we hope to reach the solution of the " riddles 
of the universe." 

The uneducated member of a civilized community is 
surrounded with countless enigmas at every step, just 
as truly as the savage. Their number, however, de- 
creases with every stride of civilization and of science ; 
and the monistic philosophy is ultimately confronted 
with but one simple and comprehensive enigma the 
" problem of substance." Still, we may find it useful 
to include a certain number of problems under that title. 
In the famous speech which Emil du Bois-Reymond de- 
livered in 1880, in the Leibnitz session of the Berlin Acad- 
emy of Sciences, he distinguished seven world-enigmas, 
which he enumerated as follows: (i) The nature of 
matter and force. (2) The origin of motion. (3) The 
origin of life. (4) The (apparently preordained) or- 
derly arrangement of nature. (5) The origin of simple 
sensation and consciousness. (6) Rational thought, 
and the origin of the cognate faculty, speech. (7) The 
question of the freedom of the will. Three of these sev- 
en enigmas are considered by the orator of the Berlin 
Academy to be entirely transcendental and insoluble 
they are the first, second, and fifth; three others 


(the third, fourth, and sixth) he considers to be capable 
of solution, though extremely difficult; as to the sev- 
enth and last " world-enigma/' the freedom of the will, 
which is the one of the greatest practical importance, 
he remains undecided. 

As my monism differs materially from that of the Ber- 
lin orator, and as his idea of the " seven great enigmas " 
has been very widely accepted, it may be useful to indi- 
cate their true position at once. In my opinion, the 
three transcendental problems (i, 2, and 5) are settled 
by our conception of substance (vide chap, xii.) ; the 
three which he considers difficult, though soluble, (3, 4, 
and 6), are decisively answered by our modern theory 
of evolution ; the seventh and last, the freedom of the 
will, is not an object for critical, scientific inquiry at all, 
for it is a pure dogma, based on an illusion, and has no 
real existence. 

The means and methods we have chosen for attain- 
ing the solution of the great enigma do not differ, on 
the whole, from those of all purely scientific investiga- 
tion firstly, experience; secondly, inference. Scien- 
tific experience comes to us by observation and experi- 
ment, which involve the activity of our sense-organs in 
the first place, and, secondly, of the inner sense-centres 
in the cortex of the brain. The microscopic elementary 
organs of the former are the sense-cells ; of the latter, 
groups of ganglionic cells. The experiences which we 
derive from the outer world by these invaluable instru- 
ments of our mental life are then moulded into ideas by 
other parts of the brain, and these, in their turn, are 
united in a chain of reasoning by association. The con- 
struction of this chain may take place in two different 
ways, which are, in my opinion, equally valuable and 
indispensable: induction and deduction. The higher 



cerebral operations, the construction of complicated 
chains of reasoning, abstraction, the formation of con- 
cepts, the completion of the perceptive faculty by the 
plastic faculty of the imagination in a word, conscious- 
ness, thought, and speculation are functions of the 
ganglionic cells of the cortex of the brain, just like the 
preceding simpler mental functions. We unite them 
all in the supreme concept of reason* 

By reason only can we attain to a correct knowledge 
of the world and a solution of its great problems. Rea- 
son is man's highest gift, the only prerogative that es- 
sentially distinguishes him from the lower animals. 
Nevertheless, it has only reached this high position by 
the progress of culture and education, by the develop- 
ment of knowledge. The uneducated man and the sav- 
age are just as little (or just as much) "rational" as 
our nearest relatives among the mammals (apes, dogs, 
elephants, etc.). Yet the opinion still obtains in many 
quarters that, besides our godlike reason, we have two 
further (and even surer !) methods of receiving knowl- 
edge emotion and revelation. We must at once dis- 
pose of this dangerous error. Emotion has nothing 
whatever to do with the attainment of truth. That 
which we prize under the name of "emotion" is an 
elaborate activity of the brain, which consists of feel- 
ings of like and dislike, motions of assent and dissent, 
impulses of desire and aversion. It may be influenced 
by the most diverse activities of the organism, by the 
cravings of the senses and the muscles, the stomach, 
the sexual organs, etc. The interests of truth are far 
from promoted by these conditions and vacillations of 
emotion ; on the contrary, such circumstances often dis- 

* As to induction and deduction, vide The Natural History of 



turb that reason which alone is adapted to the pursuit 
of truth, and frequently mar its perceptive power. No 
cosmic problem is solved, or even advanced, by the cere- 
bral function we call emotion. And the same must be 
said of the so-called "revelation/' and of the " truths 
of faith" which it is supposed to communicate; they 
are based entirely on a deception, consciously or uncon- 
sciously, as we shall see in the sixteenth chapter. 

We must welcome as one of the most fortunate steps 
in the direction of a solution of the great cosmic prob- 
lems the fact that of recent years there is a growing 
tendency to recognize the two paths which alone lead 
thereto experience and thought, or speculation to be 
of equal value, and mutually complementary. Phi- 
losophers have come to see that pure speculation- 
such, for instance, as Plato and Hegel employed for 
the construction of their idealist systems does not 
lead to knowledge of reality. On the other hand, sci- 
entists have been convinced that mere experience 
such as Bacon and Mill, for example, made the basis 
of their realist systems is insufficient of itself for a 
complete philosophy. For these two great paths of 
knowledge, sense-experience and rational thought, are 
two distinct cerebral functions; the one is elaborated 
by the sense-organs and the inner sense-centres, the 
other by the thought-centres, the great "centres of 
association in the cortex of the brain/' which lie be- 
tween the sense - centres. (Cf. cc. vii. and x.) True 
knowledge is only acquired by combining the activity 
of the two. Nevertheless, there are still many philos- 
ophers who would construct the world out of their 
own inner consciousness, and who reject our empirical 
science precisely because they have no knowledge of 
the real world. On the other hand, there are many 



scientists who still contend that the sole object of sci- 
ence is " the knowledge of facts, the objective investi- 
gation of isolated phenomena "; that " the age of phi- 
losophy " is past, and science has taken its place.* This 
one-sided over-estimation of experience is as dangerous 
an error as the converse exaggeration of the value of 
speculation. Both channels of knowledge are mutual- 
ly indispensable. The greatest triumphs of modern 
science the cellular theory, the dynamic theory of 
heat, the theory of evolution, and the law of substance 
are philosophic achievements ; not, however, the fruit 
of pure speculation, but of an antecedent experience of 
the widest and most searching character. 

At the commencement of the nineteenth century the 
great idealistic poet, Schiller, gave his counsel to both 
groups of combatants, the philosophers and the sci- 
entists : 

" Does strife divide your efforts no union bless your toil ? 
Will truth e'er be delivered if ye your forces rend ?" 

Since then the situation has, happily, been profoundly 
modified; while both schools, in their different paths, 
have pressed onward towards the same high goal, 
they have recognized their common aspiration, and 
they draw nearer to a knowledge of the truth in mutual 
covenant. At the end of the nineteenth century we 
have returned to that monistic attitude which our 
greatest realistic poet, Goethe, had recognized from its 
very commencement to be alone correct and fruitful.^ 

* Rudolph Virchow, Die Grundung der Berliner Universitdt und 
der Uebergang aus dent philosophischen in das naturwissenschaft- 
liche Zeitalter. (Berlin ; 1893.) 

f Cf . chap. iv. of my General Morphology, 1866 ; Kritik der 
natururissenschaftlichen Methoden. 



All the different philosophical tendencies may, from 
the point of view of modern science, be ranged in two 
antagonistic groups; they represent either a dualistic 
or a monistic interpretation of the cosmos. The for- 
mer is usually bound up with teleological and idealis- 
tic dogmas, the latter with mechanical and realistic 
theories. Dualism, in the widest sense, breaks up the 
universe into two entirely distinct substances the 
material world and an immaterial God, who is repre- 
sented to be its creator, sustainer, and ruler. Monism, 
on the contrary (likewise taken in its widest sense), 
recognizes one sole substance in the universe, which 
is at once * God and nature " ; body and spirit (or mat- 
ter and energy) it holds to be inseparable. The extra- 
mundane God of dualism leads necessarily to theism; 
and the intra-mundane God of the monist leads to 

The different ideas of monism and materialism, and 
likewise the essentially distinct tendencies of theoreti- 
cal and practical materialism, are still very frequently 
confused. As this and other similar cases of confu- 
sion of ideas are very prejudicial, .and give rise to in- 
numerable errors, we shall make the following brief 
observations, in order to prevent misunderstanding : 

I. Pure monism is identical neither with the theo- 
retical materialism that denies the existence of spirit, 
and dissolves the world into a heap of dead atoms, nor 
with the theoretical spiritualism (lately entitled " ener- 
getic " spiritualism by Ostwald) which rejects the no- 
tion of matter, and considers the world to be a specially 
arranged group of " energies " or immaterial natural 

II. On the contrary, we hold, with Goethe, that 
"matter cannot exist and be operative without spirit, 



nor spirit without matter." We adhere firmly to the 
pure, unequivocal monism of Spinoza: Matter, or in- 
finitely extended substance, and spirit (or energy), or 
sensitive and thinking substance, are the two funda- 
mental attributes or principal properties of the all- 
embracing divine essence of the world, the universal 
substance. (Cf. chap, xii.i 


Fundamental Importance of Anatomy Human Anatomy Hip- 
pocrates, Aristotle, Galen, Vesalius Comparative Anatomy 
Georges Cuvier Johannes Miiller Karl Gegenbaur His- 
tologyThe Cellular Theory Schleiden and Schwann Kol- 
liker Virchow Man a Vertebrate, a Tetrapod, a Mammal, 
a Placental, a Primate Prosimiae and Simise The Catar- 
rhinse Papiomorphic and Anthropomorphic Apes Essential 
Likeness of Man and the Ape in Corporal Structure. 

A LL biological research, all investigation into the 
** forms and vital activities of organisms, must 
first deal with the visible body, in which the mor- 
phological and physiological phenomena are ob- 
served. This fundamental rule holds good for man 
just as much as for all other living things. More- 
over, the inquiry must not confine itself to mere ob- 
servation of the outer form; it must penetrate to the 
interior, and study both the general plan and the mi- 
nute details of the structure. The science which pur- 
sues this fundamental investigation in the broadest 
sense is anatomy. 

The first stimulus to an inquiry into the human 
frame arose, naturally, in medicine. As it was usually 
practised by the priests in the older civilizations, we 
may assume that these highest representatives of the 
education of the time had already acquired a certain 



amount of anatomical knowledge two thousand years 
before Christ, or even earlier. We do not, however, 
find more exact observations, founded on the dissection 
of mammals, and applied, by analogy, to the human 
frame, until we come to the Greek scientists of the sixth 
and fifth centuries before Christ Empedocles (of Ag- 
rigentum) and Democritus (of Abdera), and especially 
the most famous physician of classic antiquity, Hip- 
pocrates (of Cos). It was from these and other sources 
that the great Aristotle, the renowned " father of natural 
history," equally comprehensive as investigator and 
philosopher, derived his first knowledge. After him 
only one anatomist of any consequence is found in an- 
tiquity, the Greek physician Claudius Galenus (of Per- 
gamus), who developed a wealthy practice in Rome in 
the second century after Christ, under the Emperor 
Marcus Aurelius. All these ancient anatomists ac- 
quired their knowledge, as a rule, not by the dissection 
of the human body itself which was then sternly for- 
bidden but by a study of the bodies of the animals 
which most closely resembled man, especially the apes ; 
they were all, indeed, comparative anatomists. 

The triumph of Christianity and its mystic theories 
meant retrogression to anatomy, as it did to all the other 
sciences. The popes were resolved above all things to 
detain humanity in ignorance ; they rightly deemed a 
knowledge of the human organism to be a dangerous 
source of enlightenment as to our true nature. During 
the long period of thirteen centuries the writings of Ga- 
len were almost the only source of human anatomy, 
just as the works of Aristotle were for the whole of nat- 
ural history. It was not until the sixteenth century, 
when the spiritual tyranny of the papacy was broken 
by the Reformation, and the geocentric theory, so in- 



timately connected with papal doctrine, was destroyed 
by the new cosmic system of Copernicus, that the 
knowledge of the human frame entered upon a new pe- 
riod of progress. The great anatomists, Vesalius (of 
Brussels), and Eustachius and Fallopius (of Modena), 
advanced the knowledge of our bodily structure so much 
by their own thorough investigations that little re- 
mained for their numerous followers to do, with regard 
to the more obvious phenomena, except the substantia- 
tion of details. Andreas Vesalius, as courageous as 
he was talented and indefatigable, was the pioneer of 
the movement ; he completed in his twenty-eighth year 
(1543) that great and systematic work De humani cor- 
poris fabrica; he gave to the whole of human anat- 
omy a new and independent scope and a more solid 
foundation. On that account he was, at a later date, 
at Madrid where he was physician to Charles V. and 
Philip II. condemned to death by the Inquisition as 
a magician. He only escaped by undertaking a pil- 
grimage to Jerusalem; in returning he suffered ship- 
wreck on the Isle of Zante, and died there in misery and 

The great merit of the nineteenth century, as far as 
our knowledge of the human frame is concerned, lies in 
the founding of two new lines of research of immense 
importance comparative anatomy and histology, or 
microscopic anatomy. The former was intimately as- 
sociated with human anatomy from the very beginning ; 
indeed, it had to supply the place of the latter so long 
because the dissection of human corpses was a crime 
visited with capital punishment that was the case even 
in the fifteenth century ! But the many anatomists of 
the next three centuries devoted themselves mainly to 
a more accurate study of the human organism. The 


elaborate science which we now call comparative anat 
omy was born in the year 1803, when the great French 
zoologist Georges Cuvier (a native of Mompelgard, in 
Alsace) published his profound Lemons sur I'anatomie 
comparee, and endeavored to formulate, for the first 
time, definite laws as to the organism of man and the 
beasts. While his predecessors among whom was. 
Goethe in 1790 had mainly contented themselves with 
comparing the skeleton of man with those of other ani- 
mals, Cuvier's broader vision took in the whole of the 
animal organization. He distinguished therein four 
great and mutually independent types : Vertebrata, Ar- 
ticulata, Mollusca, and Radiata. This advance was 
of extreme consequence for our " question of all ques- 
tions," since it clearly brought out the fact that man 
belonged to the vertebral type, and differed fundamen 
tally from all the other types. It is true that the keen- 
sighted Linne had already, in his Systema Naturae, 
made a great step in advance by assigning man a defi- 
nite place in the class of mammals ; he had even drawn 
up the three groups of half -apes, apes, and men (Lemur, 
simia, and homo) in the order of primates. But his 
keen, systematic mind was not furnished with that pro- 
found empirical foundation, supplied by comparative 
anatomy, which Cuvier was the first to attain. Fur- 
ther developments were added by the great comparative 
anatomists of our own century Friedrich Meckel 
(Halle), Johannes Miiller (Berlin), Richard Owen, T. 
Huxley, and Karl Gegenbaur (Jena, subsequently Hei- 
delberg). The last-named, in applying the evolution- 
ary theory, which Darwin had just established, to com- 
parative anatomy, raised his science to the front rank 
of biological studies. The numerous comparative an- 
atomical works of Gegenbaur are, like his well-known 


Manual of Hitman Anatomy, equally distinguished 
by a thorough empirical acquaintance with their im- 
mense multitudes of facts, and by a comprehensive con- 
trol of his material, and its philosophic appreciation in 
the evolutionary sense. His recent Comparative An- 
atomy of the Vertebrata establishes the solid foundation 
on which our conviction of the vertebral character of 
man in every aspect is chiefly based. 

Microscopic anatomy has been developed, in the 
course of the present century, in a very different fash- 
ion from comparative anatomy. At the beginning of 
the century (1802) a French physician, Bichat, made an 
attempt to dissect the organs of the human body into 
their finer constituents by the aid of the microscope, 
and to show the connection of these various tissues 
(hista, or tela). This first attempt led to little result, 
because the scientist was ignorant of the one common 
element of all the different tissues. This was first dis- 
covered (1838) in the shape of the cell, in the plant 
world, by Matthias Schleiden, and immediately, after- 
wards proved to be the same in the animal world by 
Theodor Schwann, the pupil and assistant of Jo- 
hannes M tiller at Berlin. Two other distinguished 
pupils of this great master, who are still living, Albert 
Kolliker and Rudolph Virchow, took up the cellular 
theory, and the theory of tissues which is founded on 
it, in the sixties, and applied them to the human or- 
ganism in all its details, both in health and disease; 
they proved that, in man and all other animals, every 
tissue is made up of the same microscopic particles, 
Ihe cells, and these "elementary organisms" are the 
real, self -active citizens which, in combinations of mill- 
ions, constitute the " cellular state," our body. All these 
spring from one simple cell, the cytula, or im- 


pregnated ovum, by continuous subdivision. The gen* 
eral structure and combination of the tissues are the 
same in man as in the other vertebrates. Among 
these the mammals, the youngest and most highly 
developed class take precedence, in virtue of certain 
special features which were acquired late. Such are, 
for instance, the microscopic texture of the hair, of the 
glands of the skin, and of the breasts, and the corpus- 
cles of the blood, which are quite peculiar to mam- 
mals, and different from those of the other verte- 
brates; man, even in these finest histological rela- 
tions, is a true mammal. 

The microscopic researches of Albert Kolliker and 
Franz Leydig (at Wurzburg) not only enlarged our 
knowledge of the finer structure of man and the beasts 
in every direction, but they were especially important 
in the light of their connection with the evolution of 
the cell and the tissue ; they confirmed the great theory 
of Carl Theodor Siebold (1845) that the lowest animals, 
the Infusoria and the Rhizopods, are unicellular or- 

Our whole frame, both in its general plan and its 
detailed structure, presents the characteristic type of 
the vertebrates. This most important and most high- 
ly developed group in the animal world was first recog- 
nized in its natural unity in 1801 by the great La- 
marck; he embraced under that title the four higher 
animal groups of Linne" mammals, birds, amphibia, 
and fishes. To these he opposed the two lower classes, 
insects and worms, as invertebrates. Cuvier (1812) 
established the unity of the vertebrate type on a firmer 
basis by his comparative anatomy. It is quite true 
that all the vertebrates, from the fish up to man, agree 
in every essential feature; they all have a firm inter- 



nal skeleton, a framework of cartilage and bone, con- 
sisting principally of a vertebral column and a skull ; 
the advanced construction of the latter presents many 
variations, but, on the whole, all may be reduced to 
the same fundamental type. Further, in all verte- 
brates the "organ of the mind," the central nervous 
system, in the shape of a spinal cord and a brain, lies 
at the back of this axial skeleton. Moreover, what 
we said of its bony environment, the skull, is also 
true of the brain the instrument of consciousness and 
all the higher functions of the mind; its construction 
and size present very many variations in detail, but 
its general characteristic structure remains always the 

We meet the same phenomenon when we compare 
the rest of our organs with those of the other verte- 
brates ; everywhere, in virtue of heredity, the original 
plan and the relative distribution of the organs remain 
the same, although, through adaptation to different 
environments, the size and the structure of particular 
sections offer considerable variation. Thus we find 
that in all cases the blood circulates in two main blood- 
vessels, of which one the aorta passes over the in- 
testine, and the other the principal vein passes un- 
derneath, and that by the broadening out of the latter 
in a very definite spot a heart has arisen ; this " ventral 
heart " is just as characteristic of all vertebrates as the 
" dorsal heart " is of the articulata and mollusca. 
Equally characteristic of all vertebrates is the early 
division of the intestinal tube into a " head-gut " (or 
gill-gut), which serves in respiration, and a " body- 
gut " (or liver-gut), which co-operates with the liver in 
digestion ; so are, likewise, the ramification of the mus- 
cular system, the peculiar structure of the urinary and 



sexual organs, and so forth. In all these anatomical 
relations man is a true vertebrate. 

Aristotle gave the name of four-footed, or tetrapoda, 
to all the higher warm-blooded animals which are dis- 
tinguished by the possession of two pairs of legs. The 
category was enlarged subsequently, and its title 
changed into the Latin " quadrupeda," when Cuvier 
proved that even " two-legged " birds and men are 
really "four-footed"; he showed that the internal 
skeleton of the four legs in all the higher land-verte- 
brates, from the amphibia up to man, was originally 
constructed after the same pattern out of a definite 
number of members. The " arm " of man and the 
"wing" of bats and birds have the same typical skele- 
ton as the foreleg of the animals which are conspicu- 
ously " four-footed." 

The anatomical unity of the fully developed skeleton 
in the four limbs of all tetrapods is very important. 
In order to appreciate it fully one has only to compare 
caref ulty the skeleton of a salamander or a frog with 
that of a monkey or a man. One perceives at once 
that the humeral zone in front and the pelvic zone be- 
hind are made up of the same principal parts as in the 
rest of the quadrupeds. We find in all cases that the 
first section of the leg proper consists of one strong 
marrow-bone (the humerus, in the forearm ; the femur, 
behind) ; the second part, on the contrary, originally 
always consists of two bones (the ulna and radius, in 
front; the fibula and tibia, behind). When we further 
compare the developed structure of the foot proper we 
are surprised to find that the small bones of which it 
is made up are also similarly arranged and distributed 
in every case: in the front limb the three groups of 
bones of the forefoot (or "hand") correspond in all 


classes of the tetrapoda: (i) the carpus, (2) the meta- 
carpus, (3) the five fingers (digiti anteriores) ; in the 
rear limb, similarly, we have always the same three 
osseous groups of the hind foot: (i) the tarsus, (2) the 
metatarsus, and (3) the five toes (digiti posterior es] . It 
was a very difficult task to reduce all these little bones 
to one primitive type, and to establish the equivalence 
(or homology) of the separate parts in all cases ; they 
present extreme variations of form and construction in 
detail, sometimes being partly fused together and losing 
their individuality. This great task was first success- 
fully achieved by the most eminent comparative anat- 
omist of our day, Karl Gegenbaur. He pointed out, 
in his Researches into the Comparative Anatomy of 
the Vertebrata (1864), how this characteristic " five-toed 
leg " of the land tetrapods originally (not before the 
Carboniferous period) arose out of the radiating fin 
(the breast-fin, or the belly- fin) of the ancient fishes. 
He had also, in his famous Researches into the Skull of 
the Vertebrata (1872), deduced the younger skull of the 
tetrapods from -the oldest cranial form among the fishes, 
that of the shark. 

It is especially remarkable that the original number 
of the toes (five) on each of the four feet, which first 
appeared in the old amphibia of the Carboniferous 
period, has, in virtue of a strict heredity, been pre- 
served even to the present day in man. Also, natural- 
ly and harmoniously, the typical construction of the 
joints, ligaments, muscles, and nerves of the two pairs 
of legs has, in the main, remained the same as in the 
rest of the "four-footed." In all these important rela- 
tions man is a true tetrapod. 

The mammals are the youngest and most advanced 
class of the vertebrates. It is true they are derived 



from the older class of amphibia, like birds and reptiles : 
yet they are distinguished from all the other tetrapods 
by a number of very striking anatomical features. Ex- 
ternally, there is the clothing of the skin with hair, and 
the possession of two kinds of skin glands the sweat 
glands and the sebaceous glands. A local develop- 
ment of these glands on the abdominal skin gave rise 
(probably during the Triassic period) to the organ which 
is especially characteristic of the class, and from which 
it derives its name the mammarium. This important 
instrument of lactation is made up of milk glands 
(mammae) and the " mammar-pouches " (folds of the 
abdominal skin) ; in its development the teats appear, 
through which the young mammal sucks its mother's 
milk. In internal structure the most remarkable feature 
is the possession of a complete diaphragm, a muscular 
wall which, in all mammals and only in mammals 
separates the thoracic from the abdominal cavity ; in 
all other vertebrates there is no such separation. The 
skull of mammals is distinguished by a number of re- 
markable formations, especially in the maxillary ap- 
paratus (the upper and lower jaws, and the temporal 
bones). Moreover, the brain, the olfactory organ, the 
heart, the lungs, the internal and external sexual or- 
gans, the kidneys, and other parts of the body present 
special peculiarities, both in general and detailed struct- 
ure, in the mammals ; all these, taken collectively, point 
unequivocally to an early derivation of the mammals 
from the older groups of the reptiles and amphibia, 
which must have taken place, at the latest, in the 
Triassic period at least twelve million years ago! 
In all these important characteristics man is a true 

' The numerous orders (12-33) which modern system- 



atic zoology distinguishes in the class of mammals 
had been arranged in 1816 (by Blainville) in three nat- 
ural groups, which still hold good as sub-classes : (i) 
the monotrema, (2) the marsupialia, and (3) the placen- 
talia. These three sub-classes not only differ in the im- 
portant respect of bodily structure and development, 
but they correspond, also, to three different historical 
stages in the formation of the class, as we shall see 
later on. The monotremes of the Triassic period were 
followed by the marsupials of the Jurassic, and these 
by the placentals of the Cretaceous. Man belongs to 
this, the youngest, sub-class ; for he presents in his or- 
ganization all the features which distinguish the pla- 
centals from the marsupials and the still older mono- 
tremes. First of all, there is the peculiar organ which 
gives a name to the placentals the placenta. It serves 
the purpose of nourishing the young mammal embryo 
for a long time during its enclosure in the mother's 
womb; it consists of blood-bearing tufts which grow 
out of the chorion surrounding the embryo, and pene- 
trate corresponding cavities in the mucous membrane 
of the maternal uterus ; the delicate skin between the 
two structures is so attenuated in this spot that the nu- 
triment in the mother's blood can pass directly into the 
blood of the child. This excellent contrivance for nour- 
ishing the embryo, which makes its first appearance at 
a somewhat late date, gives the foetus the opportunity 
of a longer maintenance and a higher development in 
the protecting womb; it is wanting in the implacen- 
talia, the two older sub-classes of the marsupials and 
the monotremes. There are, likewise, other anatomical 
features, particularly the higher development of the 
brain and the absence of the marsupial bone, which 
raise the placentals above all their implacental ances- 



tors. In all these important particulars man is a true 

The very varied sub-class of the placentals has been 
recently subdivided into a great number of orders ; they 
are usually put at from ten to sixteen, but when we in- 
clude the important extinct forms which have been re- 
cently discovered the number runs up to from twenty to 
twenty-six. In order to facilitate the study of these 
numerous orders, and to obtain a deeper insight into 
their kindred construction, it is very useful to form them 
into great natural groups, which I have called " le- 
gions." In my latest attempt* to arrange the advanced 
system of placentals in phylogenetic order I have sub- 
stituted eight of these legions for the twenty-six orders, 
and shown that these may be reduced to four main 
groups. These, in turn, are traceable to one common 
ancestral group of all the placentals, their fossil ances- 
tors, the prochoriata of the Cretaceous period. These 
are directly connected with the marsupial ancestors of 
the Jurassic period. We will only specify here, as the 
most important living representatives of these four 
main groups, the rodentia, the ungulata, the carnivora, 
and the primates. To the legion of the primates be- 
long the prosimise (half -apes), the simiae (real apes), 
and man. All the members of these three orders agree 
in many important features, and are at the same time 
distinguished by these features from the other twenty- 
three orders of placentals. They are especially con- 
spicuous for the length of their bones, which were orig- 
inally adapted to their arboreal manner of life. Their 
hands and feet are five-fingered, and the long fingers 
are excellently suited for grasping and embracing the 

* Systematische Phylogenie, 1896, part iii., pp. 490, 494, and 496. 


branches of trees ; they are provided, either partially or 
completely, with nails, but have no claws. The denti- 
tion is complete, containing all four classes incisors, 
canine, premolars, and molars. Primates are also dis- 
tinguished from all the other placentals by important 
features in the special construction of the skull and the 
brain; and these are the more striking in proportion 
to their development and the lateness of their appear- 
ance in the history of the earth. In all these important 
anatomical features our human organism agrees with 
that of all the other primates : man is a true primate. 
An impartial and thorough comparison of the bodily 
structure of the primates forces us to distingiush two 
orders in this most advanced legion of the mammalia 
half-apes (prosimiae or hemipitheci) and apes (simiae 
or pithed). The former seem in every respect to be the 
lower and older, the latter to be the higher and younger 
order. The womb of the half-ape is still double, or two- 
horned, as it is in all the other mammals. In the true 
ape, on the contrary, the right and left wombs have 
completely amalgamated ; they blend into a pear- 
shaped womb, which the human mother possesses be- 
sides the ape. In the skull of the apes, just as in that 
of man, the orbits of the eyes are completely sepa- 
rated from the temporal cavities by an osseous par- 
tition; in the prosimiae this is either entirely want- 
ing or very imperfect. Finally, the cerebrum of the 
prosimia is either quite smooth or very slightly fur- 
rowed, and proportionately small; that of the true 
ape is much larger, and the gray bed especially, the or- 
gan of higher psychic activity, is much more developed ; 
the characteristic convolutions and furrows appear on 
its surface exactly in proportion as the ape approaches 
to man. In these and other important respects, par- 



ticularly in the construction of the face and the hands, 
man presents all the anatomical marks of a true ape. 

The extensive order of apes was divided by Geoffroi, 
in 1812, into two sub-orders, which are still universally 
accepted in systematic zoology New World and Old 
World monkeys, according to the hemisphere they re- 
spectively inhabit. The American " New World " mon- 
keys are called Platyrrhinae (flat-nosed) ; their nose is 
flat, and the nostrils divergent, with a broad partition. 
The " Old World " monkeys, on the contrary, are called 
collectively Catarrhinae (narrow-nosed) ; their nostrils 
point downward, like man's, and the dividing cartilage 
is narrow. A further difference between the two groups 
is that the tympanum is superficial in the platyrrhinae, 
but lies deeper, inside the petrous bone, in the catar- 
rhinae ; in the latter a long and narrow bony passage 
has been formed, while in the former it is still short and 
wide, or even altogether wanting. Finally, we have a 
much more important and decisive difference between 
the two groups in the circumstance that all the Old 
World monkeys have the same teeth as man i.e., 
twenty deciduous and thirty-two permanent teeth (two 
incisors, one canine, two premolars, and three molars in 
each half of the jaw). The New World monkeys, on 
the other hand, have an additional premolar in each 
half-jaw, or thirty-six teeth altogether. The fact that 
these anatomical differences of the two simian groups 
are universal and conspicuous, and that they harmonize 
with their geographical distribution in the two hemi- 
spheres, fully authorizes a sharp systematic division 
of the two, as well as the phylogenetic conclusion that 
for a very long period (for more than a million years) 
the two sub-orders have been developing quite inde- 
pendently of each other in the western and eastern 



hemispheres. That is a most important point in view 
of the geneaology of our race; for man bears all the 
marks of a true catarrhina ; he has descended from 
some extinct member* of this sub-order in the Old World. 
The numerous types of catarrhinae which still sur- 
vive in Asia and Africa have been formed into two sec- 
tions for some time the tailed, doglike apes (the cyno- 
pitheci) and the tailless, manlike apes (the anthropo- 
morpha). The latter are much nearer to man than the 
former, not only in the absence of a tail and in the gen- 
eral build of the body (especially of the head), but also 
on account of certain features which are unimportant 
in themselves but very significant in their constancy. 
The sacrum of the anthropoid ape, like that of man, is 
made up of the fusion of five vertebrae ; that of the cyno- 
pithecus consists of three (more rarely four) sacral ver- 
tebras. The premolar teeth of the cynopitheci are great- 
er in length than breadth ; those of the anthropomorpha 
are broader than they are long; and the first molar 
has four protuberances in the former, five in the latter. 
Furthermore, the outer incisor of the lower jaw is broad- 
er than the inner one in the manlike apes and man ; in 
the doglike ape it is the smaller. Finally, there is a 
special significance in the fact, established by Selenka 
in 1890, that the anthropoid apes share with man the 
peculiar structure of the discoid placenta, the decidua 
reflexa, and the pedicle of the allantois. In fact, even 
a superficial comparison of the bodily structure of the 
anthropomorpha which still survive makes it clear that 
both the Asiatic (the orang-outang and the gibbous 
ape) and the African (the gorilla and chimpanzee) rep- 
resentatives of this group are nearer to man in build 
than any of the cynopitheci. Under the latter group 
we include the dog-faced papiomorpha, the baboon, and 



the long-tailed monkey, at a very low stage. The ana- 
tomical difference between these low papiomorpha and 
the most highly developed anthropoid apes is greater 
in every respect, whatever organ we take for compari- 
son, than the difference between the latter and man. 
This instructive fact was established with great pene- 
tration by the anatomist Robert Hartmann, in his work 
on The Anthropoid Apes'* he proposed to divide the 
order of Simiae in a new way namely, into the two 
great groups of primaria (man and the anthropoid ape) 
and the simiae proper, or pithed (the rest of the catar- 
rhinse and all the platyrrhinae). In any case, we have 
a clear proof of the close affinity of man and the anthro- 
poid ape. 

Thus comparative anatomy proves to the satisfaction 
of every unprejudiced and critical student the signifi- 
cant fact that the body of man and that of the anthro- 
poid ape are not only peculiarly similar, but they are 
practically one and the same in every important respect. 
The same two hundred bones, in the same order and 
structure, make up our inner skeleton ; the same three 
hundred muscles effect our movements ; the same hair 
clothes our skin ; the same groups of ganglionic cells 
build up the marvellous structure of our brain; the 
same four chambered heart is the central pulsometer in 
our circulation ; the same thirty-two teeth are set in the 
same order in our jaws ; the same salivary, hepatic, and 
gastric glands compass our digestive process ; the same 
reproductive organs insure the maintenance of our race. 

It is true that we find, on close examination, certain 
minor differences in point of size and shape in most 
of the organs of man and the ape ; but we discover the 

* Translated in the International Science Series, 1872. 


same, or similar, differences between the higher and 
lower races of men, when we make a careful compari- 
son even, in fact, in a minute comparison of the va- 
rious individuals of our own race. We find no two per- 
sons who have exactly the same size and form of nose, 
ears, eyes, and so forth. One has only to compare at- 
tentively these special features in many different per- 
sons in any large company to convince one's self of the 
astonishing diversity of their construction and the in- 
finite variability of specific forms. Not infrequently 
even two sisters are so much unlike as to make their 
origin from the same parents almost incredible. Yet 
all these individual variations do not weaken the sig- 
nificance of the fundamental similarity of structure; 
they are traceable to certain minute differences in the 
growth of the individual features. 


Development of Physiology in Antiquity and the Middle Ages: 
Galen Experiment and Vivisection Discovery of the Cir- 
culation of the Blood by Harvey Vitalism : Haller Teleo- 
logical and Vitalistic Conception of Life Mechanical and 
Monistic View of the Physiological Processes Comparative 
Physiology in the Nineteenth Century : Johannes Miiller 
Cellular Physiology : Max Verworn Cellular Pathology : 
Virchow Mammal Physiology Similarity of all Vital Ac- 
tivity in Man and the Ape 

IT is only in the nineteenth century that our knowl- 
edge of human life has attained the dignity of a 
genuine, independent science ; during the course of the 
century it has developed into one of the highest, most 
interesting, and most important branches of knowledge. 
This " science of the vital functions/' physiology, had, 
it is true, been regarded at a much earlier date as a de- 
sirable, if not a necessary, condition of success in medi- 
cal treatment, and had been constantly associated with 
anatomy, the science of the structure of the body. But 
it was only much later, and much more slowly, than the 
latter that it could be thoroughly studied, as it had to 
contend with much more serious difficulties. 

The idea of life, as the opposite of death, naturally 
became the subject of speculation at a very early age. 
In the living man, just as in other living animals, there 



were certain peculiar changes, especially movements, 
which were wanting in lifeless nature: spontaneous 
locomotion, the beat of the heart, the drawing of the 
breath, speech, and so forth. But the discrimination 
of such " organic movements " from similar phenomena 
in inorganic bodies was by no means easy, and was 
frequently impossible ; the flowing stream, the flicker- 
ing flame, the rushing wind, the falling rock, seemed 
to man to exhibit the same movements. It was quite 
natural that primitive man should attribute an inde- 
pendent life to these " dead " bodies. He knew no 
more of the real sources of movement in the one case 
than in the other. 

We find the earliest scientific observations on the 
nature of man's vital functions (as well as on his struct- 
ure) in the Greek natural philosophers and physicians 
of the sixth and fifth centuries before Christ. The 
best collection of the physiological facts which were 
known at that time is to be found in the Natural His- 
tory of Aristotle; a great number of his assertions 
were probably taken from Democritus and Hippocrates. 
The school of the latter had already made attempts to 
explain the mystery ; it postulated as the ultimate 
source of life in man and the beasts a volatile " spirit 
of life" (Pneuma) ; and Erasistratus (280 B.C.) al- 
ready drew a distinction between the lower and the 
higher " spirit of life," the pneuma zoticon in the heart 
and the pneuma psychicon in the brain. 

The credit of gathering these scattered truths into 
unity, and of making the first attempt at a systematic 
physiology, belongs to the great Greek physician 
Galen ; we have already recognized in him the first 
great anatomist of antiquity (cf. p. 23). In his re- 
searches into the organs of the body he never lost sight 



of the question of their vital activity, their functions ; 
and even in this direction he proceeded by the same 
comparative method, taking for his principal study 
the animals which approach nearest to man. What- 
ever he learned from these he applied directly to man. 
He recognized the value of physiological experiment ; 
in his vivisection of apes, dogs, and swine he made a 
number of interesting experiments. Vivisection has 
been made the object of a violent attack in recent years, 
not only by the ignorant and narrow-minded, but by 
theological enemies of knowledge and by perfervid 
sentimentalists ; it is, however, one of the indispensa- 
ble" methods of research into the nature of life, and has 
given us invaluable information on the most impor- 
tant questions. This was recognized by Galen seven- 
teen hundred years ago. 

Galen reduces all the different functions of the body 
to three groups, which correspond to the three forms of 
the pneuma, or vital spirit. The pneuma psychicon 
the soul which resides in the brain and nerves, is the 
cause of thought, sensation, and will (voluntary move- 
ment) ; the pneuma zoticon the heart is responsible 
for the beat of the heart, the pulse, and the temperature ; 
the pneuma physicon, seated in the liver, is the source 
of the so-called vegetative functions, digestion and as- 
similation, growth and reproduction. He especially 
emphasized the renewal of the blood in the lungs, and 
expressed a hope that we should some day succeed in 
isolating the permanent element in the atmosphere 
the pneuma, as he calls it which is taken into the 
blood in respiration. More than fifteen centuries 
elapsed before this pneuma oxygen was discovered 
by Lavoisier. 

In human physiology, as well as in anatomy, the 


great system of Galen was for thirteen centuries the 
Codex aureus, the inviolable source of all knowledge. 
The influence of Christianity, so fatal to scientific 
culture, raised the same insuperable obstacles in this 
as in every other branch of secular knowledge. Not a 
single scientist appeared from the third to the six- 
teenth century who dared to make independent research 
into man's vital activity, and transcend the limits of 
the Galenic system. It was not until the sixteenth 
century that experiments were made in that direction 
by a number of distinguished physicians and anato- 
mists (Paracelsus, Servetus, Vesalius, and others). In 
1628 Harvey published his great discovery of the cir- 
culation of the blood, and showed that the heart is a 
pump, which drives the red stream unceasingly through 
the connected system of arteries and veins by a rhyth- 
mic, unconscious contraction of its muscles. Not less 
important were Harvey's researches into the procrea- 
tion of animals, as a result of which he formulated the 
well-known law : " Every living thing comes from an 
egg " (omne vivum ex ovo). 

The powerful impetus which Harvey gave to physio- 
logical observation and experiment led to a great num- 
ber of discoveries in the sixteenth and seventeenth 
centuries. These were co-ordinated for the first time 
by the learned Albrecht Haller about the middle of the 
last century; in his great work, Elementa Physiolo- 
giae, he established the inherent importance of the sci- 
ence, independently of its relation to practical medi- 
cine. In postulating, however, a special " sensitive 
force or sensibility " for neural action, and a special 
"irritability" for muscular movement, Haller gave 
strong support to the erroneous idea of a specific "vital 
force " (vis vitalis). 



For more than a century afterwards, from the mid- 
dle of the eighteenth until the middle of the nineteenth 
century, medicine and (especially) physiology were 
dominated by the old idea that a certain number of the 
vital processes may be traced to physical and chemical 
causes, but that others are the outcome of a special vital 
force which is independent of physical agencies. How- 
ever much scientists differed in their conceptions of its i 
nature and its relation to the "soul," they were all 
agreed as to its independence of, and essential distinc- 
tion from, the chemico-physical forces of ordinary " mat- 
ter " ; it was a self-contained force (archaeus), unknown 
in inorganic nature, which compelled ordinary forces 
into its service. Not only the distinctly psychical activ- 
ity, the sensibility of the nerves and the irritability of 
the muscles, but even the phenomena of sense activity, 
of reproduction, and of development seemed so won- 
derful and so mysterious in their sources that it was im- 
possible to attribute them to simple physical and chem- 
ical processes. As the free activity of the vital force 
was purposive and conscious, it led, in philosophy, to 
a complete teleology; especially did this seem ^indis- 
putable when even the "critical" philosopher Kant 
had acknowledged, in his famous critique of the tele- 
ological position, that, though the mind's authority 
to give a mechanical interpretation of all phenomena is 
theoretically unlimited, yet its actual capacity for such 
interpretation does not extend to the phenomena of or- 
ganic life; here we are compelled to have recourse to 
a purposive therefore supernatural principle. This 
divergence of the vital phenomena from the mechanical 
processes of life became, naturally, more conspicuous 
as science advanced in the chemical and physical ex- 
planation of the latter. The circulation of the blood 



and a number of other phenomena could be traced to 
mechanical agencies ; respiration and digestion were 
attributable to chemical processes like those we find 
in inorganic nature. On the other hand, it seemed im- 
possible to do this with the wonderful performances of 
the nerves and muscles, and with the characteristic life 
of the mind ; the co-ordination of all the different forces 
in the life of the individual seemed also beyond such a 
mechanical interpretation. Hence there arose a com- 
plete physiological dualism an essential distinction 
was drawn between inorganic and organic nature, be- 
tween mechanical and vital processes, between material 
force and life force, between the body and the soul. At 
the beginning of the nineteenth century this vitalism 
was firmly established in France by Louis Dumas, 
and in Germany by Reil. Alexander Humboldt had 
already published a poetical presentation of it in 1795, 
in his narrative of the Legend of Rhodes ; it is repeated, 
with critical notes, in his Views of Nature. 

In the first half of the seventeenth century the famous 
philosopher Descartes, starting from Harvey's discov- 
ery of the circulation of the blood, put forward the idea 
that the body of man, like that of other animals, is 
merely an intricate machine, and that its movements 
take place under the same mechanical laws as the 
movements of an automaton of human construction. 
It is true that Descartes, at the same time, claimed for 
man the exclusive possession of a, perfectly indepen- 
dent, immaterial soul, and held that its subjective ex- 
perience, thought, was the only thing in the world of 
which we have direct and certain cognizanze (" Cogito, 
ergo sum 1 '). Yet this dualism did not prevent him 
from doing much to advance our knowledge of the me- 
chanical life processes in detail. Borelli followed ( 1 660) 



with a reduction of the movements of the animal body 
to purely physical laws, and Sylvius endeavored, about 
the same time, to give a purely chemical explanation of 
the phenomena of digestion and respiration ; the former 
founded the iatromechanical, the latter the iatrochem- 
ical, school of medicine. However, these rational ten- 
dencies towards a natural, mechanical explanation of 
the phenomena of life did not attain to a universal ac- 1 
ceptance and application; in the course of the eigh- 
teenth century they fell entirely away before the advance 
of teleological vitalism. The final disproof of the latter 
and a return to mechanism only became possible with 
the happy growth of the new science of comparative 
physiology in the forties of the present century. 

Our knowledge of the vital functions, like our knowl- 
edge of the structure of the human body, was originally 
obtained, for the most part, not by direct observation of 
the human organism itself, but by a study of the more 
closely related animals among the vertebrates, espe- 
cially the mammals. In this sense the very earliest 
beginning of human anatomy and physiology was 
"comparative." But the distinct science of "compar- 
ative physiology," which embraces the whole sphere of 
life phenomena, from the lowest animal up to man, is 
a triumph of the nineteenth century. Its famous cre- 
ator was Johannes M tiller, of Berlin (born, the son of a 
shoemaker, at Coblentz, in 1801). For fully twenty- 
five years from 1833 to 1858 this most versatile and 
most comprehensive biologist of our age evinced an ac- 
tivity at the Berlin University, as professor and in- 
vestigator, which is only comparable with the asso- 
ciated work of Haller and Cuvier. Nearly every one 
of the great biologists who have taught and worked in 
Germany for the last sixty years was, directly or in- 
5 45 


directly, a pupil of Johannes Mtiller. Starting from the 
anatomy and physiology of man, he soon gathered all 
the chief groups of the higher and lower animals within 
his sphere of comparison. As, moreover, he compared 
the structure of extinct animals with the living, and 
the healthy organism with the diseased, endeavoring 
to bring together all the phenomena of life in a truly 
philosophic fashion, he attained a biological knowledge 
far in advance of his predecessors. 

The most valuable fruit of these comprehensive stud- 
ies of Johannes Miiller was his Manual of Human Phys- 
iology. This classical work contains much more than 
the title indicates ; it is the sketch of a comprehensive 
" comparative biology." It is still unsurpassed in re- 
spect of its contents and range of investigation. In 
particular, we find the methods of observation and ex- 
periment applied in it as masterfully as the philosophic 
processes of induction and deduction. Miiller was orig- 
inally a vitalist, like all the physiologists of his time. 
Nevertheless, the current idea of a vital force took a 
novel form in his speculations, and gradually trans- 
formed itself into the very opposite. For he attempted 
to explain the phenomena of life mechanically in every 
department of physiology. His "transfigured" vital 
force was not above the physical and chemical laws of 
the rest of nature but entirely bound up with them. It 
was, in a word, nothing more than life itself that is, 
the sum of all the movements which we perceive in the 
living organism. He sought especially to give them 
the same mechanical interpretation in the life of the 
senses and of the mind as in the working of the mus- 
cles ; the same in the phenomena of circulation, res- 
piration, and digestion as in generation and develop- 
ment. Miiller ! s success was chiefly due to the fact 



that he always began with the simplest life phenomena 
of the lowest animals, and followed them step by step 
in their gradual development up to the very highest, to 
man. In this his method of critical comparison proved 
its value both from the physiological and from the ana- 
tomical point of view. Johannes Miiller is, moreover, 
the only great scientist who has equally cultivated 
these two branches of research, and combined them 
with equal brilliancy. Immediately after his death 
his vast scientific kingdom fell into four distinct prov- 
inces, which are now nearly always represented by 
four or more chairs human and comparative anat- 
omy, pathological anatomy, physiology, and the his- 
tory of evolution. This sudden division of Miiller's 
immense realm of learning in 1858 has been compared 
to the dissolution of the empire which Alexander the 
Great had consolidated and ruled. 

Among the many pupils of Johannes Miiller who, 
either during his lifetime or after his death, labored 
hard for the advancement of the various branches of 
biology, one of the most fortunate if not the most im- 
portant was Theodor Schwann. When the able bot- 
anist Schleiden, in 1838, indicated the cell as the com- 
mon elementary organ of all plants, and proved that 
all the different tissues of the plant are merely combi- 
nations of cells, Johannes Miiller recognized at once the 
extraordinary possibilities of this important discovery. 
He himself sought to point out the same composition 
in various tissues of the animal body for instance, in 
the spinal cord of vertebrates and thus led his pupil, 
Schwann, to extend the discovery to all the animal tis- 
sues. This difficult task was accomplished by Schwann 
in his Microscopic Researches into the Accordance in 
the Structure and Growth of Plants and Animals (1839). 



Thus was the foundation laid of the " cellular theory/' 
the profound importance of which, both in physiology 
and anatomy, has become clearer and more widely 
recognized in each subsequent year. Moreover, it was 
shown by two other pupils of Johannes Miiller that the 
activity of all organisms is, in the ultimate analysis, 
the activity of the components of their tissues, the mi- 
croscopic cells these were the able physiologist Ernst 
Briicke, of Vienna, and the distinguished histologist 
Albert Kolliker, of Wiirzburg. Briicke correctly de- 
nominated the cells the " elementary organisms/' and 
showed that, in the body of man and of all other ani- 
mals, they are the only actual, independent factors of 
the life process. Kolliker earned special distinction, 
not only in the construction of the whole science of 
histology, but particularly by showing that the ani- 
mal ovum and its products are simple cells. 

Still, however widely the immense importance of the 
cellular theory for all biological research was acknowl- 
edged, the " cellular physiology " which is based on it 
only began an independent development very recently. 
In this Max Verworn (of Jena) earned a twofold dis- 
tinction. In his Psycho-physiological Studies of the 
Protistae (1889) he showed, as a result of an ingenious 
series of experimental researches, that the " theory of 
a cell-soul " which I put forward in 1866" is completely 
established by an accurate study of the unicellular pro- 
tozoa, and that "the psychic phenomena of the pro- 
tistae form the bridge which unites the chemical pro- 
cesses of inorganic nature with the mental life of the 
highest animals." Verworn has further developed 
these views, and based them on the modern theory of 

*Zell-Seelen und Seelen-Zellen. Ernst Haeckel, Gesammelte 
popular e Vortrage. I. Heft. 1878. 



evolution, in his General Physiology. This distin- 
guished work returns to the comprehensive point of 
view of Johannes Miiller, in opposition to the one- 
sided and narrow methods of those modern physiolo- 
gists who think to discover the nature of the vital phe- 
nomena by the exclusive aid of chemical and physical 
experiments. Verworn showed that it is only by Miil- 
ler's comparative method and by a profound study of 
the physiology of the cell that we can reach the higher 
stand-point which will give us a comprehensive survey 
of the wonderful realm of the phenomena of life. Only 
thus do we become convinced that the vital processes in 
man are subject to the same physical and chemical 
laws as those of all other animals. 

The fundamental importance of the cellular theory 
for all branches of biology was made clear in the second 
half of the nineteenth century, not only by the rapid 
progress of morphology and physiology, but also by 
the entire reform of that biological science which has 
always been deemed most important on account of its 
relation to practical medicine pathology, or the sci- 
ence of disease. Many even of the older physicians 
were convinced that human diseases were natural phe- 
nomena, like all other manifestations of life, and should 
be studied scientifically, like other vital functions. Par- 
ticular schools of medicine the latrophysical and the 
latrochemical had already, in the seventeenth cen- 
tury, attempted to trace the sources of disease to certain 
physical and chemical changes. However, the imper- 
fect condition of science at that period precluded any 
lasting results of these efforts. Many of the older 
theories, which sought the nature of disease in super- 
natural and mystical causes, were almost universally 
accepted down to the middle of the nineteenth century. 



It was then that Rudolf Virchow, another pupil oi 
Miiller, conceived the happy idea of transferring the 
cellular theory from the healthy to the diseased organ- 
ism ; he sought in the more minute metamorphoses of 
the diseased cells and the tissues they composed the 
true source of those larger changes which, in the form 
of disease, threaten the living organism with peril and 
death. Especially during the seven years of his pro- 
fessorship at Wiirzburg (1849-56) Virchow pursued his 
great task with such brilliant results that his Cellular 
Pathology (published in 1858) turned, at one stroke, the 
whole of pathology and the dependent science of prac- 
tical medicine into new and eminently fruitful paths. 
This reform of medicine is significant for our present 
purpose in that it led us to a monistic and purely scien- 
tific conception of disease. In sickness, no less than 
in health, man is subject to the same eternal "iron 
laws" of physics and chemistry as all the rest of the 
organic world. 

Among the numerous classes of animals which 
modern zoology distinguishes the mammals occupy 
a pre-eminent position, not only on morphological 
grounds, but also for physiological reasons. As man 
belongs to the class of mammals (see p. 27) by every por- 
tion of his frame, we must expect him to share his 
characteristic functions with the rest of the mammals. 
Such we find to be the case. The circulation of the 
blood and respiration are accomplished in man under 
precisely the same laws and in the same manner as in 
all the other mammals and in these alone ; they are 
determined by the peculiar structure of their heart and 
lungs. In mammals only is all the arterial blood con- 
ducted from the left ventricle of the heart to the body 
by one, the left, branch of the aorta, while in birds it 



passes along the right branch, and in reptiles along 
both branches. The blood of mammals is distinguish- 
ed from that of any other vertebrate by the circum- 
stance that its red cells have lost their nucleus (by 
reversion). The respiratory movements are effected 
largely by the diaphragm in this class of animals 
alone, because only in them does it form a complete 
partition between the pectoral and abdominal cavities. 
Special importance, however, in this highest class of 
animals, attaches to the production of milk in the 
breasts (mammae), and to the peculiar method of the 
rearing of the young, which entails the supplying of 
the offspring with the mother's milk. As this nutri- 
tive process reacts most powerfully on the other vi- 
tal functions, and the maternal affection of mam- 
mals must have arisen from this intimate form of 
rearing, the name of the class justly reminds us of its 
great importance. In millions of pictures, most of 
them produced by painters of the highest rank, the 
" madonna with the child" is revered as the purest 
and noblest type of maternal love the instinct which 
is found in its extreme form in the exaggerated ten- 
derness of the mother-ape. 

As the apes approach nearest to man of all the mam- 
mals in point of structure, we shall expect to hear the 
same of their vital functions ; and that we find to be 
the case. Everybody knows how closely the habits, 
the movements, the sense activity, the mental life, and 
the parental customs of apes resemble those of man. 
Scientific physiology proves the same significant r6- 
semblance in other less familiar processes, particularly 
in the working of the heart, the division of the breasts, 
and the sexual life. In the latter connection it is es- 
pecially noteworthy that the mature females of many 

5 1 


kinds of apes suffer a periodical discharge of blood 
from the womb, which corresponds to the menstrua- 
tion of the human female. The secretion of the milk 
in the glands and the suctorial process also take place 
in the female ape in precisely the same fashion as in 

Finally, it is of especial interest that the speech of 
apes seems on physiological comparison to be a stage 
in the formation of articulate human speech. Among 
living apes there is an Indian species which is musical ; 
the hylobates syndactylus sings a full octave in per- 
fectly pure, harmonious half - tones. No impartial 
philologist can hesitate any longer to admit that our 
elaborate rational language has been slowly and 
gradually developed out of the imperfect speech of 
our Pliocene simian ancestors. 


The Older Embryology The Theory of Preformation The The- 
ory of Scatulation : Haller and Leibnitz The Theory of Epi- 
genesis : C. F. Wolff The Theory of Germinal Layers : Carl 
Ernst Baer Discovery of the Human Ovum : Remak, Kolli- 
ker The Egg-Cell and the Sperm-Cell The Theory of the 
Gastrgea Protozoa and Metazoa The Ova and the Sperma- 
tozoa : Oscar Hertwig Conception Embryonic Develop- 
ment in Man Uniformity of the Vertebrate Embryo The 
Germinal Membranes in Man The Amnion, the Serolemma, 
and the Allantois The Formation of the Placenta and the 
"After-Birth " The Decidua and the Funiculus Umbilicalis 
The Discoid Placenta of Man and the Ape. 

/COMPARATIVE ontogeny, or the science of the de- 
^* velopment of the individual animal, is a child of 
the nineteenth century in even a truer sense than com- 
parative anatomy and physiology. How is the child 
formed in the mother's womb ? How do animals 
evolve from ova? How does the plant come forth 
from the seed? These pregnant questions have oc- 
cupied the thoughtful mind for thousands of years. 
Yet it is only seventy years since the embryologist 
Baer pointed out the correct means and methods for 
penetrating into the mysteries of embryonic life ; it is 
only forty years since Darwin, by his reform of the 
theory of descent, gave us the key which should open 
the long-closed door, and lead to a knowledge of em- 



bryonic agencies. As I have endeavored to give a 
complete, popular presentation of this very interest- 
ing but difficult study in the first section of my An- 
thropogeny, I will confine myself here to a brief survey 
and discussion of the most important phenomena. Let 
us first cast a historical glance at the older ontogeny, 
and the theory of preformation which is connected 
with it. 

The classical works of Aristotle, the many-sided 
" father of science," are the oldest known scientific 
sources of embryology, as we found them to be for 
comparative anatomy. Not only in his great natural 
history, but also in a special small work, Five Books 
on the Generation and Development of Animals, the 
great philosopher gives us a host of interesting facts, 
adding many observations on their significance; it 
was not until our own days that many of them were 
fully appreciated, and, indeed, we may say, discovered 
afresh. Naturally, many fables and errors are mixed 
up with them ; it was all that was known at that time 
of the hidden growth of the human germ. Yet during 
the long space of the next two thousand years the 
slumbering science made no further progress. It was 
not until the commencement of the seventeenth cen- 
tury that there was a renewal of activity. In 1600 the 
Italian anatomist Fabricius ab Aquapendente pub- 
lished at Padua the first pictures and descriptions of 
the embryos of man and some of the higher animals ; 
in 1687 the famous Marcello Malpighi, of Bologna, a 
distinguished pioneer alike in zoology and botany, 
published the first consistent exposition of the growth 
of the chick in the hatched egg. 

All these older scientists were possessed with the 
idea that the complete body, with all its parts, was 



already contained in the ovum of animals, only it was 
so minute and transparent that it could not be detected ; 
that, therefore, the whole development was nothing 
more than a growth, or an " unfolding," of the parts 
that were already " infolded " (involutae). This erro- 
neous notion, almost universally accepted until the .be- 
ginning of the present century, is called the " preforma- 
tion theory " ; sometimes it is called the " evolution the- 
ory " (in the literal sense of " unfolding ") ; but the 
latter title is accepted by modern scientists for the very 
different theory of "transformation." 

Closely connected with the preformation theory, and 
as a logical consequence of it, there arose in the last 
century a further theory which keenly interested all 
thoughtful biologists the curious " theory of scatu- 
lation." As it was thought that the outline of the en- 
tire organism, with all its parts, was present in the egg, 
the ovary of the embryo had to be supposed to contain 
the ova of the following generation ; these, again, the ova 
of the next, and so on in infinitum 1 On that basis the 
distinguished physiologist Haller calculated that God 
had created together, 6000 years ago on the sixth day 
of his creatorial labors the germs of 200,000,000,000 
men, and ingeniously packed them all in the ovary of 
our venerable mother Eve. Even the gifted philos- 
opher Leibnitz fully accepted this conclusion, and em- 
bodied it in his monadist theory ; and as, on his theory, 
soul and body are in eternal, inseparable companion- 
ship, the consequence had to be accepted for the soul ; 
" the souls of men have existed in organized bodies in 
their ancestors from Adam downward that is, from 
the very beginning of things." 

In the month of November, 1759, a young doctor of 
twenty-six years, Caspar Friedrich Wolff (son of a Berlin 



tailor), published his dissertation for the degree at Halle, 
under the title, Theoria Generationis. Supported by a 
series of most laborious and painstaking observations, 
he proved the entire falsity of the dominant theories 
of preformation and scatulation. In the hatched egg 
there is at first no trace of the coming chick and its or- 
gans ; instead of it we find on top of the yolk a small, 
circular, white disk. This thin " germinal disk " be- 
comes gradually round, and then breaks up into four 
folds, lying upon each other, which are the rudiments 
of the four chief systems of organs the nervous sys- 
tem above, the muscular system underneath, the vas- 
cular system (with the heart), and, finally, the aliment- 
ary canal. Thus, as Wolff justly remarked, the 
embryonic development does not consist in an unfold- 
ing of the preformed organs, but in a series of new con- 
structions ; it is a true epigenesis. One part arises after 
another, and all make their appearance in a simple 
form, which is very different from the later structure. 
This only appears after a series of most remarkable 
formations. Although this great discovery one of 
the most important of the eighteenth century could 
be directly proved by a verification of the facts Wolff 
had observed, and although the " theory of genera- 
tion " which was founded on it was in reality not a the- 
ory at all, but a simple fact, it met with no sympathy 
whatever for half a century. It was particularly re- 
tarded by the high authority of Haller, who fought it 
strenuously with the dogmatic assertion that " there is 
no such thing as development : no part of the animal 
body is formed before another; all were created to- 
gether." Wolff, who had to go to St. Petersburg, was 
long in his grave before the forgotten facts he had ob- 
served were discovered afresh by Oken at Jena, in 1806. 



After Wolff's " epigenesis theory " had been estab- 
lished by Oken and Neckel (whose important work on 
the development of the alimentary canal was translated 
from Latin into German), a number of young German 
scientists devoted themselves eagerly to more accurate 
embryological research. The most important and suc- 
cessful of these was Carl Ernst Baer. His principal 
work appeared in 1828, with the title, History of the 
Development of Animals : Observations and Reflections. 
Not only the phenomena of the formation of the germ 
are clearly illustrated and fully described in it, but it 
adds a number of very pregnant speculations. In par- 
ticular, the form of the embryo of man and the mammals 
is correctly presented, and the vastly different devel- 
opment of the lower invertebrate animals is also con- 
sidered. The two leaflike layers which appear in the 
round germ disk of the higher vertebrates first divide, 
according to Baer, into two further layers, and these 
four germinal layers are transformed into four tubes, 
which represent the fundamental organs the skin 
layer, the muscular layer, the vascular layer, and the 
mucous layer. Then, by very complicated evolution- 
ary processes, the later organs arise, in substantially 
the same manner, in man and all the other vertebrates. 
The three chief groups of invertebrates, which in their 
turn differ widely from each other, have a very different 

One of the most important of Baer's many discov- 
eries was the finding of the human ovum. Up to that 
time the little vesicles which are found in great num- 
bers in the human ovary and in that of all other mam- 
mals had been taken for the ova. Baer was the first 
to prove, in 1827, that the real ova are enclosed in these 
vesicles the " Graafian follicles " and much smaller, 



being tiny spheres i-i20th inch in diameter, visible to 
the naked eye as minute specks under favorable con- 
ditions. He discovered likewise that from this tiny 
ovum of the mammal there develops first a character- 
istic germ globule, a hollow sphere with liquid contents, 
the wall of which forms the slender germinal mem- 
brane, or blastoderm. 

Ten years after Baer had given a firm foundation to 
embryological science by his theory of germ layers a 
new task confronted it on the establishment of the cellu- 
lar theory in 1838. What is the relation of the ovum 
and the layers which arise from it to the tissues and 
cells which compose the fully developed organism ? The 
correct answer to this difficult question was given about 
the middle of this century by two distinguished pupils 
of Johannes Muller Robert Remak, of Berlin, and 
Albert Kolliker, of Wiirzburg. They showed that the 
ovum is at first one simple cell, and that the many ger- 
minal globules, or granules, which arise from it by re- 
peated segmentation, are also simple cells. From this 
mulberry-like group of cells are constructed first the 
germinal layers, and subsequently by differentiation, 
or division of labor, all the different organs. Kolliker 
has the further merit of showing that the seminal fluid 
of male animals is also a mass of microscopic cells. 
The active pin-shaped " seed-animalcules," or sperma- 
tozoa, in it are merely ciliated cells, as I first proved in 
the case of the seed-filaments of the sponge in 1866. 
Thus it was proved that both the materials of genera- 
tion, the male sperm and the female ova, fell in with the 
cellular theory. That was a discovery of which the 
great philosophic significance was not appreciated until 
a much later date, on a close study of the phenomena 
of conception in 1875. 



All the older studies in embryonic development con- 
cern man and the higher vertebrates, especially the em- 
bryonic bird, since hens' eggs are the largest and most 
convenient objects for investigation, and are plentiful 
enough to facilitate experiment; we can hatch them 
in the incubator, as well as by the natural function of 
the hen, and so observe from hour to hour, during the 
space of three weeks, the whole series of formations, 
from the simple germ cell to the complete organism. 
Even Baer had only been able to gather from such ob- 
servations the fact that the different classes of verte- 
brates agreed in the characteristic form of the germ 
layers and the growth of particular organs. In the 
innumerable classes of invertebrates, on the other hand 
that is, in the great majority of animals the embry- 
onic development seemed to run quite a different course, 
and most of them seemed to be altogether without true 
germinal layers. It was not until about the middle of 
the century that such layers were found in some of the 
invertebrates. Huxley, for instance, found them in the 
medusae in 1849, and Kolliker in the cephalopods in 
1844. Particularly important was the discovery of 
Kowalewsky (1886) that the lowest vertebrate the lan- 
celot, or amphioxus is developed in just the same man- 
ner (and a very original fashion it is) as an inverte- 
brate, apparently quite remote, tunicate, the sea-squirt, 
or ascidian. Even in some of the worms, the radiata 
and the articulata, a similar formation of the germinal 
layers was pointed out by the same observer. I myself 
was then (since 1886) occupied with the embryology of 
the sponges, corals, medusae, and siphonophorae, and, 
as I found the same formation of two primary germ 
layers everywhere in these lowest classes of multicellu- 
lar animals, I came to the conclusion that this impor- 



tant embryonic feature is common to the entire animal 
world. The circumstance that in the sponges and the 
cnidaria (polyps, medusae, etc.) the body consists for a 
long time, sometimes throughout life, merely of two 
simple layers of cells, seemed to me especially signifi- 
cant. Huxley had already (1849) compared these, in 
the case of the medusae, with the two primary germinal 
layers of the vertebrates. On the ground of these ob- 
servations and comparisons I then, in 1872, in my Phi- 
losophy of the Calcispongiae, published the " theory of 
the gastraea," of which the following are the essential 
points : 

I. The whole animal world falls into two essentially 
different groups, the unicellular primitive animals (Pro- 
tozoa) and the multicellular animals with complex tis- 
sues (Metazoa). The entire organism of the protozoon 
(the rhizopods of the infusoria) remains throughout life 
a single simple cell (or occasionally a loose colony of 
cells without the formation of tissue, a coenobium). The 
organism of the metazoon, on the contrary, is only uni- 
cellular at the commencement, and is subsequently 
built up of a number of cells which form tissues. 

II. Hence the method of reproduction and develop- 
ment is very different in each of these great categories 
of animals. The protozoa usually multiply by non- 
sexual means, by fission, gemmation, or spores ; they 
have no real ova and no sperm. The metazoa, on the 
contrary, are divided into male and female sexes, and 
generally propagate sexually, by means of true ova, 
which are fertilized by the male sperm. 

III. Hence, further, true germinal layers, and the 
tissues which are formed from them, are found only 
in the metazoa ; they are entirely wanting in the pro- 



IV. In all the metazoa only two primary layers ap- 
pear at first, and these have always the same essential 
significance ; from the outer layer the external skin and 
the nervous system are developed ; from the inner layer 
are formed the alimentary canal and all the other or- 

V. I called the germ, which always arises first from 
the impregnated ovum, and which consists of these two 
primary layers, the " gut-larva," or the gastrula ; its 
cup -shaped body with the two layers encloses origi- 
nally a simple digestive cavity, the primitive gut (the 
progaster or archenteron) , and its simple opening is the 
primitive mouth (the prostoma or blastoporus) . These 
are the earliest organs of the multicellular body, and 
the two cell layers of its enclosing wall, simple epithelia, 
are its earliest tissues ; all the other organs and tissues 
are a later and secondary growth from these. 

VI. From this similarity, or homology, of the gas- 
trula in all classes of compound animals I drew the con- 
clusion, in virtue of the biogenetic law (p. 81), that all 
the metazoa come originally from one simple ancestral 
form, the gastraea, and that this ancient (Laurentian), 
long-extinct form had the structure and composition of 
the actual gastrula, in which it is preserved by heredity. 

VII. This phylogenetic conclusion, based on the 
comparison of ontogenetic facts, is confirmed by the 
circumstance that there are several of these gastraeades 
still in existence (gastraemaria, cyemaria, physemaria, 
etc.), and also some ancient forms of other animal 
groups whose organization is very little higher (the 
olynthus of the sponges, the hydra, or common fresh- 
water polyp, of the cnidaria, the convoluta and other 
cryptocsela, or worms of the simplest type, of the pla- 

6 61 


VIII. In the further development of the various 
tissue-forming animals from the gastrula we have to 
distinguish two principal groups The earlier and 
lower types (the coelenteria or acoelomia) have no body 
cavity, no vent, and no blood ; such is the case with 
the gastraeades, sponges, cnidaria, and platodes. The 
later and higher types (the caelomaria or bilateria), on 
the other hand, have a true body cavity, and generally 
blood and a vent ; to these we must refer the worms 
and the higher types of animals which were evolved 
from these later on, the echinodermata, mollusca, artic- 
ulata, tunicata, and vertebrata. 

Those are the main points of my "gastraea theory" ; 
I have since enlarged the first sketch of it (given in 
1872), and have endeavored to substantiate it in a series 
of " Studies on the gastraea theory " (1873-84). Al- 
though it was almost universally rejected at first, and 
fiercely combated for ten years by many authorities, 
it is now (and has been for the last fifteen years) ac- 
cepted by nearly all my colleagues. Let us now see 
what far-reaching consequences follow from it, and 
from the evolution of the germ, especially with regard 
to our great question, "the place of man in nature." 

The human ovum, like that of all other animals, is 
a single cell, and this tiny globular egg cell (about the 
I20th of an inch in diameter) has just the same charac- 
teristic appearance as that of all other viviparous or- 
ganisms. The little ball of protoplasm is surrounded 
by a thick, transparent, finely reticulated membrane, 
called the zona pellucida ; even the little, g'obular, 
germinal vesicle (the cell-nucleus), which is enclosed 
in the protoplasm (the cell-body), is of the same size 
and the same qualities as in the rest of the mammals. 
The same applies to the active spermatozoa of the 



male, the minute, threadlike, ciliated cells of which 
millions are found in every drop of the seminal fluid ; 
on account of their lifelike movements they were pre- 
viously taken to be forms of life, as the name indicates 
(spermatozoa sperm animals). Moreover, the or- 
igin of both these important sexual cells in their re- 
spective organs is the same in man as in the other 
mammals ; both the ova in the ovary of the female and 
the spermatozoa in the spermarium of the male arise 
in the same fashion they always come from cells, 
which are originally derived from the coelous epithe- 
lium, the layer of cells which clothes the cavity of the 

The most important moment in the life of every man, 
as in that of all other complex animals, is the moment 
in which he begins his individual existence; it is the 
moment when the sexual cells of both parents meet 
and coalesce for the formation of a single simple cell. 
This new cell, the impregnated egg cell, is the indi- 
vidual stem cell (the cytula), the continued segmenta- 
tion of which produces the cells of the germinal layers 
and the gastrula. With the formation of this cytula, 
hence in the process of conception itself, the existence 
of the personality, the independent individual, com- 
mences. This ontogenic fact is supremely important, 
for the most far-reaching conclusions may be drawn 
from it. In the first place, we have a clear perception 
that man, like all the other complex animals, inherits 
all his personal characteristics, bodily and mental, 
from his parents; and, further, we come to the mo- 
mentous conclusion that the new personality which 
arises thus can lay no claim to " immortality." 

Hence the minute processes of conception and sexual 
generation are of the first importance. We are, how- 



ever, only familiar with their details since 1875, when 
Oscar Hertwig, my pupil and fellow-traveller at that 
time, began his researches into the impregnation of the 
egg of the sea-urchin at Ajaccio, in Corsica. The 
beautiful capital of the island in which Napoleon the 
Great was born, in 1769, was also the spot in which the 
mysteries of animal conception were carefully studied 
for the first time in their most important aspects. Hert- 
wig found that the one essential element in conception 
is the coalescence of the two sexual cells and their nu- 
clei. Only one out of the millions of male ciliated cells 
which press round the ovum penetrates to its nucleus. 
The nuclei of both cells, of the spermatozoon and of 
the ovum, drawn together by a mysterious force, which 
we take to be a chemical sense-activity, related to smell, 
approach each other and melt into one. Thus, by the 
sensitive perception of the sexual nuclei, following 
upon a kind of " erotic chemicotropism," a new cell is 
formed, which unites in itself the inherited qualities of 
both parents; the nucleus of the spermatozoon con- 
veys the paternal features, the nucleus of the ovum 
those of the mother, to the stem cell, from which the 
child is to be developed. That applies both to the bodily 
and to the mental characteristics. 

The formation of the germinal layers by the repeated 
division of the stem cell, the growth of the gastrula 
and of the later germ structures which succeed it, take 
place in man in just the same manner as in the other 
higher mammals, under the peculiar conditions which 
differentiate this group from the lower vertebrates. In 
the earlier stages of development these special charac- 
ters of the placentalia are not to be detected. The sig- 
nificant embryonic or larval form of the chordula, 
which succeeds the gastrula, has substantially the 


same structure in all vertebrates; a simple straight 
rod, the dorsal cord, lies lengthways along the main 
axis of the shield-shaped body the " embryonic shield" ; 
above the cord the spinal marrow develops out of the 
outer germinal layer, while the gut makes its appear- 
ance underneath. Then, on both sides, to the right 
and left of the axial rod, appear the segments of the 
" pro-vertebrae " and the outlines of the muscular plates, 
with which the formation of the members of the verte- 
brate body begins. The gill-clefts appear on either 
side of the fore-gut; they are the openings of the 
gullet, through which, in our primitive fish-ancestors, 
the water which had entered at the mouth for breath- 
ing purposes made its exit at the sides of the head. By 
a tenacious heredity these gill-clefts, which have no 
meaning except for our fish-like aquatic ancestors, are 
still preserved in the embryo of man and all the other 
vertebrates. They disappear after a time. Even after 
the five vesicles of the embryonic brain appear in the 
head, and the rudiments of the eyes and ears at the 
sides, and after the legs sprout out at the base of the 
fish-like embryo, in the form of two roundish, flat buds, 
the foetus is still so like that of other vertebrates that 
it is indistinguishable from them. 

The substantial similarity in outer form and inner 
structure which characterizes the embryo of man and 
other vertebrates in this early stage of development is 
an embryological fact of the first importance ; from it, 
by the fundamental law of biogeny, we may draw the 
most momentous conclusions. There is but one ex- 
planation of it heredity from a common parent form. 
When we see that, at a certain stage, the embryos of 
man and the ape, the dog and the rabbit, the pig and 
the sheep, although recognizable as higher vertebrates, 



cannot be distinguished from each other, the fact can 
only be elucidated by assuming a common parentage. 
And this explanation is strengthened when we follow 
the subsequent divergence of these embryonic forms. 
The nearer two animals are in their bodily structure, 
and, therefore, in the scheme of nature, so much the 
longer do we find their embryos to retain this resem- 
blance, and so much the closer do they approach each 
other in the ancestral tree of their respective group, so 
much the closer is their genetic relationship. Hence it 
is that the embryos of man and the anthropoid ape re- 
tain the resemblance much later, at an advanced stage 
of development, when their distinction from the em- 
bryos of other mammals can be seen at a glance. I have 
illustrated this significant fact by a juxtaposition of 
corresponding stages in the development of a number 
of different vertebrates in my Natural History of Crea- 
tion and in my Anthropogeny. 

The great phylogenetic significance of the resem- 
blance we have described is seen, not only in the com- 
parison of the embryos of vertebrates, but also in the 
comparison of their protective membranes. All ver- 
tebrates of the three higher classes reptiles, birds, and 
mammals are distinguished from the lower classes 
by the possession of certain special fetal membranes, 
the amnion and the serolemma. The embryo is en- 
closed in these membranes, or bags, which are full of 
water, and is thus protected from pressure or shock. 
This provident arrangement probably arose during the 
Permian period, when the oldest reptiles, the prorep- 
tilia, the common ancestors of all the amniotes (animals 
with an amnion), completely adapted themselves to a 
life on land. Their direct ancestors, the amphibia, and 
the fishes are devoid of these foetal membranes; they 



woulc have been superfluous to these inhabitants of 
the water. With the inheritance of these protective 
coverings are closely connected two other changes in 
the amniotes: firstly, the entire disappearance of the 
gills (while the gill arches and clefts continue to be in- 
herited as " rudimentary organs ") ; secondly, the con- 
struction of the allantois. This vesicular bag, filled 
with water, grows out of the hind-gut in the embryo of 
all the amniotes, and is nothing else than an enlarge- 
ment of the bladder of their amphibious ancestors. 
From its innermost and inferior section is formed sub- 
sequently the permanent bladder of the amniotes, while 
the larger outer part shrivels up. Usually this has an 
important part to play for a long time as the respiratory 
organ of the embryo, a number of large blood-vessels 
spreading out over its inner surface. The formation 
of the membranes, the amnion and the serolemma, and 
of the allantois, is just the same, and is effected by the 
same complicated process of growth, in man as in all 
the other amniotes ; man is a true amniote. 

The nourishment of the foetus in the maternal womb 
is effected, as is well known, by a peculiar organ, richly 
supplied with blood at its surface, called the placenta. 
This important nutritive organ is a spongy, round disk, 
from six to eight inches in diameter, about an inch thick, 
and one or two pounds in weight ; it is separated after 
the birth of the child, and issues as the " after-birth." 
The placenta consists of two very different parts, the 
foetal and the maternal part. The latter contains high- 
ly developed sinuses, which retain the blood conveyed 
to them by the arteries of the mother. On the other 
hand, the foetal placenta is formed by innumerable 
branching tufts or villi, which grow out of the outer sur- 
face of the allantois, and derive their blood from the um- 


bilical vessels. The hollow, blood-filled villi of the 
foetal placenta protrude into the sinuses of the maternal 
placenta, and the slender membrane between the two 
is so attenuated that it offers no impediment to the direct 
interchange of material through the nutritive blood- 
stream (by osmosis). 

In the older and lower groups of the placentals the 
entire surface of the chorion is covered with a number 
of short villi; these " chorion-villi " take the form of 
pit-like depressions of the mucous membrane of the 
mother, and are easily detached at birth. That hap- 
pens in most of the ungulata (the sow, camel, mare, 
etc.), the cetacea, and the prosimiae; these "mallo- 
placentalia " (with a diffuse placenta) have been de- 
nominated the indeciduata. The same formation is 
present in man and the other placentals in the begin- 
ning. It is soon modified, however, as the villi on one 
part of the chorion are withdrawn ; while on the other 
part they grow proportionately stronger, and unite in- 
timately with the mucous membrane of the womb. It 
is in consequence of this intimate blending that a por- 
tion of the uterus is detached at birth, and carried away 
with loss of blood. This detachable membrane the 
decidua is a characteristic of the higher placentalia, 
which have, consequently, been grouped under the title 
of deciduata ; to that category belong the carnassia, 
rodentia, simise, and man. In the carnassia and some 
of the ungulata (the elephant, for instance) the placenta 
takes the form of a girdle, hence they are known as the 
zonoplacentalia ; in the rodentia, the insectivora (the 
mole and the hedge-hog), the apes, and man, it takes 
the form of a disk. 

Even ten years ago the majority of embryologists 
thought that man was distinguished by certain pecu- 



liarities in the form of the placenta namely, by the pos- 
session of what is called the decidua reflexa, and by a 
special formation of the umbilical chord which unites 
the decidua to the foetus. It was supposed that the 
rest of the placentals, including the apes, were without 
these special embryonic structures. The funiculus 
umbilicalis is a smooth, cylindrical cord, from sixteen 
to twenty-three inches long, and as thick as the little 
finger. It forms the connecting link between the foetus 
and the maternal placenta, since it conducts the nutri- 
tive vessels from the body of the foetus to the placenta ; 
it comprises, besides, the pedicle of the allantois and 
the yelk-sac. The yelk-sac in the human case forms 
the greater portion of the germinal vesicle during the 
third week of gestation ; but it shrivels up afterwards 
so that it was formerly entirely missed in the mature 
foetus. Yet it remains all the time in a rudimentary 
condition, and may be detected even after birth as the 
little umbilical vesicle. Moreover, even the vesicular 
structure of the allantois disappears at an early stage 
in the human case; with a deflection of the amnion, 
it gives rise to the pedicle. We cannot enter here into 
a discussion of the complicated anatomical and embry- 
ological relations of these structures. I have described 
and illustrated them in my Anthropogeny (twenty-third 

The opponents of evolution still appealed to these 
" special features " of human embryology, which were 
supposed to distinguish man from all the other mam- 
mals, even so late as ten years ago. But in 1890 Emil 
Selenka proved that the same features are found in the 
anthropoid apes, especially in the orang (satyr us), while 
the lower apes are without them. Thus Huxley's pithe- 
cometra thesis was substantiated once more : " The 


differences between man and the great apes are not so 
great as are those between the manlike apes and the 
lower monkeys." The supposed " evidences against the 
near blood-relationship of man and the apes" proved, 
on a closer examination of the real circumstances, to 
be strong reasons in favor of it. 

Every scientist who penetrates with open eyes into 
this dark but profoundly interesting labyrinth of our 
embryonic development, and who is competent to com- 
pare it critically with that of the rest of the mammals, 
will find in it a most important aid towards the eluci- 
dation of the descent of our species. For the various 
stages of our embryonic development, in the character 
of palingenetic phenomena of heredity, cast a brilliant 
light on the corresponding stages of our ancestral tree, 
in accordance with the great law of biogeny. But even 
the cenogenetic phenomena of adaptation, the formation 
of the temporary foetal organs the characteristic foetal 
membranes, and especially the placenta gives us suf- 
ficiently definite indications of our close genetic relation- 
ship with the primates. 


Origin of Man Mythical History of Creation Moses and Linne 
The Creation of Permanent Species The Catastrophic The- 
ory : Cuvier Transformism : Goethe Theory of Descent: 
Lamarck Theory of Selection : Darwin Evolution (Phy- 
logeny) Ancestral Trees General Morphology Natural 
History of Creation Systematic Phylogeny Fundamental 
Law of Biogeny Anthropogeny Descent of Man from the 
Ape Pithecoid Theory The Fossil Pithecanthropus of Du- 

THE youngest of the great branches of the living tree 
of biology is the science we call biological evolu- 
tion, or phytogeny. It came into existence much later, 
and under much more difficult circumstances, than its 
natural sister, embryonic evolution or ontogeny. The 
object of the latter was to attain a knowledge of the 
mysterious processes by which the individual organ- 
ism, plant or animal, developed from the egg. Phy- 
logeny has to answer the much more obscure and 
difficult question : * What is the origin of the different 
organic species of plants and animals?" 

Ontogeny (embryology and metamorphism) could 
follow the empirical method of direct observation in the 
solution of its not remote problem ; it needed but to fol- 
low, day by day and hour by hour, the visible changes 
which the foetus experiences during a brief period in 
the course of its development from the ovum. Much 

7 1 


more difficult was the remote problem of phylogeny; 
for the slow processes of gradual construction, which 
effect the rise. of new species of animals and plants, go 
on imperceptibly during thousands and even millions 
of years. Their direct observation is possible only 
within very narrow limits ; the vast majority of these 
historical processes can only be known by direct in- 
ference by critical reflection, and by a comparative 
use of empirical sciences which belong to very different 
fields of thought, palaeontology, ontogeny, and mor- 
phology. To this we must add the immense opposition 
which was everywhere made to biological evolution on 
account of the close connection between questions of 
organic creation and supernatural myths and religious 
dogmas. For these reasons it can easily be under- 
stood how it is that the scientific existence of a true the- 
ory of origins was only secured, amid fierce controversy, 
in the course of the last forty years. 

Every serious attempt that was made before the be- 
ginning of the nineteenth century to solve the problem 
of the origin of species lost its way in the mythological 
labyrinth of the supernatural stories of creation. The 
efforts of a few distinguished thinkers to emancipate 
themselves from this tyranny and attain to a natural- 
istic interpretation proved unavailing. A great vari- 
ety of creation myths arose in connection with their re- 
ligion in all the ancient civilized nations. During the 
Middle Ages triumphant Christendom naturally arro- 
gated to itself the sole right of pronouncing on the ques- 
tion; and, the Bible being the basis of the structure 
of the Christian religion, the whole story of creation 
was taken from the book of Genesis. Even Carl Linne, 
the famous Swedish scientist, started from that basis 
when, in 1735, in his classical Systema Naturae, he 



made the first attempt at a systematic arrangement, 
nomenclature, and classification of the innumerable 
objects in nature. As the best practical aid in that at- 
tempt he introduced the well-known double or binary 
nomenclature; to each kind of animals and plants he 
gave a particular specific name, and added to it the 
wider-reaching name of the genus. A genus served 
to unite the nearest related species ; thus, for instance, 
Linne grouped under the genus " dog " (cams), as dif- 
ferent species, the house-dog (cam's familiar is), the 
jackal (cants aureus), the wolf (cam's lupus) the fox 
(canis vulpes), etc. This binary nomenclature imme- 
diately proved of such great practical assistance that 
it was universally accepted, and is still always followed 
in zoological and botanical classification. 

But the theoretical dogma which Linne himself con- 
nected with his practical idea of species was fraught 
with the gravest peril to science. The first question 
which forced itself on the mind of the thoughtful sci- 
entist was the question as to the nature of the concept 
of species, its contents, and its range. And the creator 
of the idea answered this fundamental question by a 
naive appeal to the dominant Mosaic legend of crea- 
tion : " Species tot sunt diver sae, quot diver sas for mas 
ab initio creavit infinitum ens " (There are just so many 
distinct species as there were distinct types created in 
the beginning by the Infinite). This theosophic dog- 
ma cut short all attempt at a natural explanation of 
the origin of species. Linn6 was acquainted only with 
the plant and animal worlds that exist to-day ; he had 
no suspicion of the much more numerous extinct spe- 
cies which had peopled the earth with their varying 
forms in the earlier period of its development. 

It was not until the beginning of the nineteenth cen- 



tury that we were introduced to these fossil animals by 
Cuvier. In his famous work on the fossil bones of the 
four-footed vertebrates he gave (1812) the first correct 
description and true interpretation of many of these fos- 
sil remains. He showed, too, that a series of very dif- 
ferent animal populations have succeeded each other 
in the various stages of the earth's history. Since Cu- 
vier held firmly to Linnets idea of the absolute perma- 
nency of species, he thought their origin could only be 
explained by the supposition that a series of great cat- 
aclysms and new creations had marked the history of 
the globe; he imagined that all living creatures were 
destroyed at the commencement of each of these terres- 
trial revolutions, and an entirely new population was 
created at its close. Although this " catastrophic the- 
ory " of Cuvier 's led to the most absurd consequences, 
and was nothing more than a bald faith in miracles, 
it obtained almost universal recognition, and reigned 
triumphant until the coming of Darwin. 

It is easy to understand that these prevalent ideas of 
the absolute unchangeability and supernatural crea- 
tion of organic species could not satisfy the more pene- 
trating thinkers. We find several eminent minds al- 
ready, in the second half of the last century, busy with 
the attempt to find a natural explanation of the " prob- 
lem of creation." Pre-eminent among them was the 
great German poet and philosopher, Wolfgang Goethe, 
who, by his long and assiduous study of morphology, 
obtained, more than a hundred years ago, a clear in- 
sight into the intimate connection of all organic forms, 
and a firm conviction of a common natural origin. 
In his famed Metamorphosis of Plants (1790) he derived 
all the different species of plants from one primitive 
type, and all their different organs from one primitive 



organ the leaf. In his vertebral theory of the skull 
he endeavored to prove that the skulls of the vertebrates 
including man were all alike made up of certain 
groups of bones, arranged in a definite structure, and 
that these bones are nothing else than transformed ver- 
tebrae. It was his penetrating study of comparative 
osteology that led Goethe to a firm conviction of the 
unity of the animal organization; he had recognized 
that the human skeleton is framed on the same funda- 
mental type as that of aU other vertebrates " built 
on a primitive plan that only deviates more or less to 
one side or other in its very constant features, and still 
develops and refashions itself daily." This remodel- 
ling, or transformation, is brought about, according to 
Goethe, by the constant interaction of two powerful 
constructive forces a centripetal force within the or- 
ganism, the " tendency to specification," and a centrif- 
ugal force without, the tendency to variation, or the 
" idea of metamorphosis " ; the former corresponds to 
what we now call heredity, the latter to the modern idea 
of adaptation. How deeply Goethe had penetrated into 
their character by these philosophic studies of the " con- 
struction and reconstruction of organic natures, "and 
how far, therefore, he must be considered the most im- 
portant precursor of Darwin and Lamarck,* may be 
gathered from the interesting passages from his works 
which I have collected in the fourth chapter of my 
Natural History of Creation. These evolutionary ideas 
of Goethe, however, like analogous ideas of Kant, 
Owen, Treviranus, and other philosophers of the com- 
mencement of the century (which we have quoted in 
the above work), did not amount to more than certain 

* Cf. E. Haeckel, The Systems of Darwin, Goethe, and Lamarck. 
Lecture given at Eisenach in 1882. 



general conclusions. They had not that great lever 
which the "natural history of creation" needed for 
its firm foundation on a criticism of the dogma of fixed 
species ; this lever was first supplied by Lamarck. 

The first thorough attempt at a scientific establish- 
ment of transformism was made at the beginning of 
the nineteenth century by the great French scientist 
Jean Lamarck, the chief opponent of his colleague, 
Cuvier, at Paris. He had already, in 1802, in his Ob- 
servations on Living Organisms, expressed the new 
ideas as to the mutability and formation of species, 
which he thoroughly established in 1809 in the two vol- 
umes of his profound work, Philosophic Zoologique. In 
this work he first gave expression to the correct idea, 
in opposition to the prevalent dogma of fixed species, 
that the organic " species " is an artificial abstraction, 
a concept of only relative value, like the wider-ranging 
concepts of genus, family, order, and class. He went 
on to affirm that all species are changeable, and have 
arisen from older species in the course of very long 
periods of time. The common parent forms from which 
they have descended were originally very simple and 
lowly organisms. The first and oldest of them arose 
by abiogenesis. While the type is preserved by hered- 
ity in the succession of generations, adaptation, on the 
other hand, effects a constant modification of the species 
by change of habits and the exercise of the various or- 
gans. Even our human organism has arisen in the 
same natural manner, by gradual transformation, from 
a group of pithecoid mammals. For all these phenom- 
ena indeed, for all phenomena both in nature and in 
the mind Lamarck takes exclusively mechanical, 
physical, and chemical activities to be the true efficient 
causes. His magnificent Philosophic Zoologique con- 



tains all the elements of a purely monistic system of 
nature on the basis of evolution. I have fully treated 
these achievements of Lamarck in the fourth chapter 
of my Anthropogeny, and in the fourth chapter of the 
Natural History of Creation. 

Science had now to wait until this great effort to give 
a scientific foundation to the theory of evolution should 
shatter the dominant myth of a " specific creation, and 
open out the path of natural " development. In this 
respect Lamarck was not more successful in resisting 
the conservative authority of his great opponent, Cuvier, 
than was his colleague and sympathizer, Geoffrey St. 
''Hilaire, twenty years later. The famous controversies 
which he had with Cuvier in the Parisian Academy in 
1830 ended with the complete triumph of the latter. 
I have elsewhere fully described these conflicts, in 
which Goethe took so lively an interest. The great ex- 
pansion which the study of biology experienced at that 
time, the abundance of interesting discoveries in com- 
parative anatomy and physiology, the establishment 
of the cellular theory, and the progress of ontogeny, 
gave zoologists and botanists so overwhelming a flood 
of welcome material to deal with that the difficult and 
obscure question of the origin of species was easily for- 
gotten for a time. People rested content with the old 
dogma of creation. Even when Charles Lyell refuted 
Cuvier's extraordinary " catastrophic theory " in his 
Principles of Geology, in 1830, and vindicated a nat- 
ural, continuous evolution for the inorganic structure 
of our planet, his simple principle of continuity found 
no one to apply it to the inorganic world. The rudi- 
ments of a natural phylogeny which were buried in 
Lamarck's works were as completely forgotten as the 
germ of a natural ontogeny which Caspar Friedrich 
7 77 


Wolff had given fifty years earlier in his Theory of 
Generation. In both cases a full half-century elapsed 
before the great idea of a natural development won 
a fitting recognition. Only when Darwin (in 1859) 
approached the solution of the problem from a differ- 
ent side altogether, and made a happy use of the 
rich treasures of empirical knowledge which had 
accumulated in the mean time, did men begin to 
think once more of Lamarck as his great precursor. 

The unparalleled success of Charles Darwin is well 
known. It shows him to-day, at the close of the cen- 
tury, to have been, if not the greatest, at least the most 
effective of its distinguished scientists. No other of 
the many great thinkers of our time has achieved so 
magnificent, so thorough, and so far-reaching a suc- 
cess with a single classical work as Darwin did in 1859 
with his famous Origin of Species. It is true that the 
reform of comparative anatomy and physiology by 
Johannes Miiller had inaugurated a new and fertile 
epoch for the whole of biology, that the establishment 
of the cellular theory by Schleiden and Schwann, the 
reform of ontogeny by Baer, and the formulation of 
the law of substance by Robert Mayer and Helmholz 
were scientific facts of the first importance; but no 
one of them has had so profound an influence on the 
whole structure of human knowledge as Darwin's 
theory of the natural origin of species. For it at once 
gave us the solution of the mystic " problem of crea- 
tion," the great " question of all questions " the prob- 
lem of the true character and origin of man himself. 

If we compare the two great founders of transform- 
ism, we find in Lamarck a preponderant inclination to 
deduction, and to forming a completely monistic scheme 
of nature ; in Darwin we have a predominant applica- 



tion of induction, and a prudent concern to establish 
the different parts of the theory of selection as firmly 
as possible on a basis of observation and experiment. 
While the French scientist far outran the then limits 
of empirical knowledge, and rather sketched the pro- 
gramme of future investigation, the English empiri- 
cist was mainly preoccupied about securing a unifying 
principle of interpretation for a mass of empirical 
knowledge which had hitherto accumulated without 
being understood. We can thus understand how it 
was that the success of Darwin was just as overwhelm- 
ing as that of Lamarck was evanescent. Darwin, 
however, had not only the signal merit of bringing 
all the results of the various biological sciences to a 
common focus in the principle of descent, and thus 
giving them a harmonious interpretation, but he also 
discovered, in the principle of selection, that direct 
cause of transformation which Lamarck had missed. 
In applying, as a practical breeder, the experience of 
artificial selection to organisms in a state of nature, 
and in recognizing in the " struggle for life " the se- 
lective principle of natural selection, Darwin created 
his momentous " theory of selection," which is what 
we properly call Darwinism. 

One of the most pressing of the many important 
tasks which Darwin proposed to modern biology was 
the reform of the zoological and botanical system. 
Since the innumerable species of animals and plants 
were not created by a supernatural miracle, but evolved 
by natural processes, their ancestral tree is their " nat- 
ural system." The first attempt to frame a system in 
this sense was made by myself in 1866, in my General 
Morphology of Organisms. The first volume of this 
work (" General Anatomy ") dealt with the " mechani- 



cal science of the developed forms " ; the second volume 
("General Evolution") was occupied with the science 
of the " developing forms." The systematic introduc- 
tion to the latter formed a " genealogical survey of the 
natural system of organisms." Until that time the 
term "evolution" had been taken to mean exclusively, 
both in zoology and botany, the development of indi- 
vidual organisms embryology, or metamorphic sci- 
ence. I established the opposite view, that this his- 
tory of the embryo (ontogeny) must be completed by a 
second, equally valuable, and closely connected branch 
of thought the history of the race (phylogeny). Both 
these branches of evolutionary science are, in my opin- 
ion, in the closest causal connection ; this arises from 
the reciprocal action of the laws of heredity and adap- 
tation ; it has a precise and comprehensive expression 
in my * fundamental law of biogeny." 

As the new views I had put forward in my General 
Morphology met with very little notice, and still less 
acceptance, from my scientific colleagues, in spite of 
their severely scientific setting, I thought I would 
make the most important of them accessible to a wider 
circle of informed readers by a smaller work, written 
in a more popular style. This was done in 1868, in 
The Natural History of Creation (a series of popular 
scientific lectures on evolution in general, and the sys- 
tems of Darwin, Goethe, and Lamarck in particular). 
If the success of my General Morphology was far below 
my reasonable anticipation, that of The Natural His- 
tory of Creation went far beyond it. In a period of 
thirty years nine editions and twelve different transla- 
tions of it have appeared. In spite of its great defects, 
the book has contributed much to the popularization 
of the main ideas of modern evolution. Still, I could 



only give the barest outlines in it of my chief object, 
the phylogenetic construction of a natural system. I 
have, therefore, given the complete proof, which is 
wanting in the earlier work, of the phylogenetic sys- 
tem in a subsequent larger work, my Systematic Phylog- 
eny (outlines of a natural system of organisms on the 
basis of their specific development). The first volume 
of it deals with the protists and plants (1894), the second 
with the invertebrate animals (1896), the third with the 
vertebrates (1895). The ancestral tree of both the 
smaller and the larger groups is carried on in this 
work as far as my knowledge of the three great 
" ancestral documents " palaeontology, ontogeny, and 
morphology qualified me to extend it. 

I had already, in my General Morphology (at the 
end of the fifth book), described the close causative 
connection which exists, in my opinion, between the 
two branches of organic evolution as one of the most 
important ideas of transformism, and I had framed a 
precise formula for it in a number of " theses on the 
causal nexus of biontic and phyletic development " : 
" Ontogenesis is a brief and rapid recapitulation of phy- 
logenesis, determined by the physiological functions of 
heredity (generation) and adaptation (maintenance)." 
Darwin himself had emphasized the great significance 
of his theory for the elucidation of embryology in 1859, 
and Fritz Miiller had endeavored to prove it as regards 
the Crustacea in the able little work, Facts and Argu- 
ments for Darwin (1864). My own task has been to 
prove the universal application and the fundamental 
importance of the biogenetic law in a series of works, 
especially in the Biology of the Calcispongiae (1872), and 
in Studies on the Gastraea Theory (1873-1884). The 
theory of the homology of the germinal layers and of 



the relations of palingenesis to cenogenesis which I have 
exposed in them has been confirmed subsequently by 
a number of works of other zoologists. That theory 
makes it possible to follow nature's law of unity in the 
innumerable variations of animal embryology ; it gives 
us for their ancestral history a common derivation from 
a simple primitive stem form. 

The far-seeing founder of the theory of descent, 
Lamarck, clearly recognized in 1809 that it was of uni- 
versal application; that even man himself, the most 
highly developed of the mammals, is derived from the 
same stem as all the other mammals ; and that this in 
its turn belongs to the same older branch of the ances- 
tral tree as the rest of the vertebrates. He had even 
indicated the agencies by which it might be possible to 
explain man's descent from the apes as the nearest re- 
lated mammals. Darwin, who was, naturally, of the 
same conviction, purposely avoided this least accepta- 
ble consequence of his theory in his chief work in 1859, 
and put it forward for the first time in his Descent of 
Man in 1871. In the mean time (1863) Huxley had 
very ably discussed this most important consequence 
of evolution in his famous Place of Man in Nature. 
With the aid of comparative anatomy and ontogeny, 
and the support of the facts of palaeontology, Huxley 
proved that the " descent of man from the ape " is a 
necessary consequence of Darwinism, and that no other 
scientific explanation of the origin of the human race 
is possible. Of the same opinion was Karl Gegenbaur, 
the most distinguished representative of comparative 
anatomy, who lifted his science to a higher level by 
a consistent and ingenious application of the theory of 

As a further consequence of the " pithecoid theory " 



(the theory of the descent of man from the ape) there 
now arose the difficult task of investigating, not only 
the nearest related mammal ancestors of man in the 
Tertiary epoch, but also the long series of the older ani- 
mal ancestors which had lived in earlier periods of the 
earth's history and been developed in the course of 
countless millions of years. I had made a start with 
the hypothetical solution of this great historic problem 
in my General Morphology ; a further development of 
it appeared in 1874 m m y Anthropogeny (first section, 
Origin of the Individual ; second section, Origin of the 
Race). The fourth, enlarged, edition of this work 
(1891) contains that theory of the development of man 
which approaches nearest, in my own opinion, to the 
still remote truth, in the light of our present knowledge 
of the documentary evidence. I was especially pre- 
occupied in its composition to use the three empirical 
" documents " palaeontology, ontogeny, and morphol- 
ogy (or comparative anatomy) as evenly and har- 
moniously as possible. It is true that my hypotheses 
were in many cases supplemented and corrected in de- 
tail by later phylogenetic research ; yet I am convinced 
that the ancestral tree of human origin which I have 
sketched therein is substantially correct. For the his- 
torical succession of vertebrate fossils corresponds com- 
pletely with the morphological evolutionary scale which 
is revealed to us by comparative anatomy and ontogeny. 
After the Silurian fishes come the dipnoi of the Devon- 
ian period the Carboniferous amphibia, the Permian 
reptilia, and the Mesozoic mammals. Of these, again, 
the lowest forms, the monotremes, appear first in the 
Triassic period, the marsupials in the Jurassic, and 
then the oldest placentals in the Cretaceous. Of the 
piacentals, in turn, the first to appear in the oldest Ter- 



tiary period (the Eocene) are the lowest primates, the 
prosimiae, which are followed by the simiae in the Mio- 
cene. Of the catarrhinae, the cynopitheci precede the 
anthropomorpha ; from one branch of the latter, dur- 
ing the Pliocene period, arises the ape-man without 
speech (the pithecanthropus alalus) ; and from him de- 
scends, finally, speaking man. 

The chain of our earlier invertebrate ancestors is 
much more difficult to investigate and much less safe 
than this tree of our vertebrate predecessors ; we have 
no fossilized relics of their soft, boneless structures, so 
palaeontology can give us no assistance in this case. 
The evidence of comparative anatomy and ontogeny, 
therefore, becomes all the more important. Since the 
human embryo passes through the same chordula-stage 
as the germs of all other vertebrates, since it evolves, 
similarly, out of two germinal layers of a gastrula, we 
infer, in virtue of the biogenetic law, the early existence 
of corresponding ancestral forms vermalia, gastrae- 
ada, etc. Most important of all is the fact that the 
human embryo, like that of all other animals, arises 
originally from a single cell ; for this " stem-cell " 
(cytula) the impregnated egg cell points indubitably 
to a corresponding unicellular ancestor, a primitive, 
Laurentian protozoon. 

For the purpose of our monistic philosophy, however, 
it is a matter of comparative indifference how the suc- 
cession of our animal predecessors may be confirmed 
in detail. Sufficient for us, as an incontestable his- 
torical fact, is the important thesis that man descends 
immediately from the ape, and secondarily from a long 
series of lower vertebrates. I have laid stress on the 
logical proof of this " pithecometra-thesis " in the sev- 
enth book of the General Morphology: "The thesis 

8 4 


that man has been evolved from lower vertebrates, and 
immediately from the simiae, is a special inference 
which results with absolute necessity from the general 
inductive law of the theory of descent." 

For the definitive proof and establishment of this 
fundamental pithecometra-thesis the palaeontological 
discoveries of the last thirty years are of the greatest 
importance ; in particular, the astonishing discoveries 
of a number of extinct mammals of the Tertiary period 
have enabled us to draw up clearly in its main outlines 
the evolutionary history of this most important class 
of animals, from the lowest oviparous monotremes up 
to man. The four chief groups of the placentals, the 
heterogeneous legions of the carnassia, the rodentia, 
the ungulata, and the primates, seem to be separated 
by profound gulfs, when we confine our attention to 
their representatives of to-day. But these gulfs are 
completely bridged, and the sharp distinctions of the 
four legions are entirely lost, when we compare their 
extinct predecessors of the Tertiary period, and when 
we go back into the Eocene twilight of history, in 
the oldest part of the Tertiary period at least three 
million years ago. There we find the great sub- 
class of the placentals, which to-day comprises more 
than two thousand five hundred species, represented 
by only a small number of little, insignificant "pro- 
placentals"; and in these prochoriata the characters 
of the four divergent legions are so intermingled and 
toned down that we cannot in reason do other than 
consider them as the precursors of those features. The 
oldest carnassia (the ictopsales), the oldest rodentia (the 
esthonychales) , the oldest ungulata (the condylarthrales) 
and the oldest primates (the lemuravales), all have the 
same fundamental skeletal structure, and the same typ- 



ical dentition of the primitive placentals, consisting of 
forty-four teeth (three incisors, one canine, four pre- 
molars, and three molars in each half of the jaw) ; all 
are characterized by the small size and the imperfect 
structure of the brain (especially of its chief part, the 
cortex, which does not become a true "organ of thought" 
until later on in the Miocene and Pliocene representa- 
tives) ; they have all short legs and five-toed, flat-soled 
feet (plantigrada) . In many cases among these oldest 
placentals of the Eocene period it was very difficult to 
say at first whether they should be classed with the 
carnassia, rodentia, ungulata, or primates; so very 
closely, even to confusion, do these four groups of the 
placentals, which diverge so widely afterwards, ap- 
proach each other at that time. Their common origin 
from a single ancestral group follows incontestably. 
These prochoriata lived in the preceding Cretaceous 
period (more than three million years ago), and were 
probably developed in the Jurassic period from a group 
of insectivorous marsupials (amphitheria) by the for- 
mation of a primitive placenta diffusa, a placenta of 
the simplest type. 

But the most important of all the recent palaeonto- 
logical discoveries which have served to elucidate the 
origin of the placentals relate to our own stem, the legion 
of primates. Formerly fossil remains of the primates 
were very scarce. Even Cuvier, the great founder of 
palaeontology, maintained until his last day (1832) that 
there were no fossilized primates ; he had himself, it is 
true, described the skull of an Eocene prosimias (adapis), 
but he had wrongly classed it with the ungulata. How- 
ever, during the last twenty years a fair number of well- 
preserved fossilized skeletons of prosimias and simiae 
have been discovered; in them we find all the chief 



intermediate members which complete the connect- 
ing chain of ancestors from the oldest prosimiae to 

The most famous and most interesting of these dis- 
coveries is the fossil ape-man of Java, the much-talked- 
of pithecanthropus erectus, found by a Dutch military 
doctor, Eugen Dubois, in 1894. It is in truth the much- 
sought " missing link/' supposed to be wanting in the 
chain of primates, which stretches unbroken from the 
lowest catarrhinae to the highest -developed man. I 
have dealt exhaustively with the significance of this dis- 
covery in the paper which I read on August 26, 1898, 
at the Fourth International Zoological Congress at 
Cambridge.* The palaeontologist, who knows the con- 
ditions of the formation and preservation of fossils, will 
think the discovery of the pithecanthropus an unusu- 
ally lucky accident. The apes, being arboreal, seldom 
came into the circumstances (unless they happened to 
fall into the water) which would secure the preserva- 
tion and petrifaction of their skeleton. Thus, by the 
discovery of this fossil man-monkey of Java the descent 
of man from the ape has become just as clear and certain 
from the palaeontological side as it was previously from 
the evidence of comparative anatomy and ontogeny. 
We now have all the principal documents which tell 
the history of our race. 

* Vide the translation of Dr. Hans Gadow : The Last Link. 
(A. &> C. Black.) 


Fundamental Importance of Psychology Its Definition and Meth 
ods Divergence of Views Thereon Dualistic and Monistic 
Psychology Relation to the Law of Substance Confusion 
of Ideas Psychological Metamorphoses : Kant, Virchow, 
Du Bois-Reymond Methods of Research of Psychic Science 
Introspective Method (Self-Observation) Exact Method (Psy- 
cho-Physics) Comparative Method (Animal Psychology) 
Psychological Change of Principles : Wundt Folk-Psychol- 
ogy and Ethnography : Bastian Ontogenetic Psychology : 
Preyer Phylogenetic Psychology : Darwin, Romanes 

FHE phenomena which are comprised under the title 
of the " life of the soul/' or the psychic activity, 
are, on the one hand, the most important and interest- 
ing, on the other the most intricate and problematical, 
of all the phenomena we are acquainted with. As 
the knowledge of nature, the object of the present 
philosophic study, is itself a part of the life of the soul, 
and as anthropology, and even cosmology, presuppose 
a correct knowledge of the "psyche," we may regard 
psychology, the scientific study of the soul, both as 
the foundation and the postulate of all other sciences. 
From another point of view it is itself a part of philoso- 
phy, or physiology, or anthropology. 

The great difficulty of establishing it on a naturalistic 
basis arises from the fact that psychology, in turn, 



presupposes a correct acquaintance with the human 
organism, especially the brain, the chief organ of 
psychic activity. The great majority of "psycholo- 
gists " have little or no acquaintance with these ana- 
tomical foundations of the soul, and thus it happens 
that in no other science do we find such contradictions 
and untenable notions as to its proper meaning and its 
essential object as are current in psychology. This 
confusion has become more and more palpable during 
the last thirty years, in proportion as the immense 
progress of anatomy and physiology has increased our 
knowledge of the structure and the functions of the 
chief psychic organ. 

What we call the soul is, in my opinion, a natural 
phenomenon ; I therefore consider psychology to be a 
branch of natural science a section of physiology. 
Consequently, I must emphatically assert from the 
commencement that we have no different methods of 
research for that science than for any of the others; 
we have in the first place observation and experiment, 
in the second place the theory of evolution, and in the 
third place metaphysical speculation, which seek to 
penetrate as far as possible into the cryptic nature of 
the phenomena by inductive and deductive reasoning. 
However, with a view to a thorough appreciation of 
the question, we must first of all put clearly before the 
reader the antithesis of the dualistic and the monistic 

The prevailing conception of the psychic activity, 
which we contest, considers soul and body to be two 
distinct entities. These two entities can exist inde- 
pendently of each other; there is no intrinsic neces- 
sity for their union. The organized body is a mortal, 
material nature, chemically composed of living proto- 


plasm and its compounds (plasma-products). The soul, 
on the other hand, is an immortal, immaterial being, 
a spiritual agent, whose mysterious activity is entirely 
incomprehensible to us. This trivial conception is, 
as such, spiritualistic, and its contradictory is, in a 
certain sense, materialistic. It is, at the same time, 
supernatural and transcendental, since it affirms the 
existence of forces which can exist and operate without 
a material basis ; it rests on the assumption that out- 
side of and beyond nature there is a " spiritual," im- 
material world, of which we have no experience, and 
of which we can learn nothing by natural means. 

This hypothetical " spirit world," which is supposed 
to be entirely independent of the material universe, 
and on the assumption of which the whole artificial 
structure of the dualistic system is based, is purely a 
product of poetic imagination ; the same must be said 
of the parallel belief in the " immortality of the soul," 
the scientific impossibility of which we must prove 
more fully later on (chap. xi.). If the beliefs which 
prevail in these credulous circles had a sound founda- 
tion, the phenomena they relate to could not be subject 
to the " law of substance " ; moreover, this single ex- 
ception to the highest law of the cosmos must have ap- 
peared very late in the history of the organic world, 
since it only concerns the " soul " of man and of the 
higher animals. The dogma of " free will," another 
essential element of the dualistic psychology, is simi- 
larly irreconcilable with the universal law of substance. 

Our own naturalistic conception of the psychic activ- 
ity sees in it a group of vital phenomena, which are de- 
pendent on a definite material substratum, like all other 
phenomena. We shall give to this material basis of 
all psychic activity, without which it is inconceivable, 



the provisional name of " psychoplasm " ; and for this 
good reason that chemical analysis proves it to be a 
body of the group we call protoplasmic bodies the al- 
buminoid carbon-combinations which are at the root 
of all vital processes. In the higher animals, which 
have a nervous system and sense-organs, " neuro- 
plasm," the nerve-material, has been differentiated out 
of psychoplasm. Our conception is, in this sense, ma- 
terialistic. It is at the same time empirical and nat- 
uralistic, for our scientific experience has never yet 
taught us the existence of forces that can dispense 
with a material substratum, or of a spiritual world 
over and above the realm of nature. 

Like all other natural phenomena, the psychic proc- 
esses are subject to the supreme, all-ruling law of sub- 
stance ; not even in this province is there a single ex- 
ception to this highest cosmological law (compare chap, 
xii.). The phenomena of the lowly psychic life of the 
unicellular protist and the plant, and of the lowest ani- 
mal forms their irritability, their reflex movements, 
their sensitiveness and instinct of self-preservation 
are directly determined by physiological action in the 
protoplasm of their cells that is, by physical and 
chemical changes which are partly due to heredity and 
partly to adaptation. And we must say just the same 
of the higher psychic activity of the higher animals and 
man, of the formation of ideas and concepts, of the mar- 
vellous phenomena of reason and consciousness; for 
the latter have been phylogenetically evolved from the 
former, and it is merely a higher degree of integration 
or centralization, of association or combination of func- 
tions which were formerly isolated, that has elevated 
them in this manner. 

The first task of every science is the clear definition 
9 1 


of the object it has to investigate. In no science, how- 
ever, is this preliminary task so difficult as in psychol- 
ogy ; and this circumstance is the more remarkable 
since logic, the science of defining, is itself a part of 
psychology. When we compare all that has been said 
by the most distinguished philosophers and scientists 
of all ages on the fundamental idea of psychology, we 
find ourselves in a perfect chaos of contradictory no- 
tions. What, really, is the " soul "? What is its re- 
lation to the " mind "? What is the inner meaning of 
" consciousness "? What is the difference between 
" sensation " and " sentiment "? What is " instinct "? 
What is the meaning of " free will "? What is " pres- 
entation"? What is the difference between "intel- 
lect " and " reason n ? What is the true nature of " emo- 
tion "? What is the relation between all these " psychic 
phenomena " and the " body "? The answers to these 
and many other cognate questions are infinitely varied ; 
not only are the views of the most eminent thinkers 
on these questions widely divergent, but even the same 
scientific authority has often completely changed his 
views in the course of his psychological development. 
Indeed, this " psychological metamorphosis " of so 
many thinkers has contributed not a little to the colos- 
sal confusion of ideas which prevails in psychology 
more than in any other branch of knowledge. 

The most interesting example of such an entire 
change of objective and subjective psychological opin- 
ions is found in the case of the most influential leader 
of German philosophy, Immanuel Kant. The young, 
severely critical Kant came to the conclusion that the 
three great buttresses of mysticism " God, freedom, 
and immortality " were untenable in the light of " pure 
reason"; the older, dogmatic Kant found that these 



three great hallucinations were postulates of " prac- 
tical reason/' and were, as such, indispensable. The 
more the distinguished modern school of " Neokant- 
ians " urges a a return to Kant " as the only possible 
salvation from the frightful jumble of modern meta- 
physics, the more clearly do we perceive the undeniable 
and fatal contradiction between the fundamental opin- 
ions of the young and the older Kant. We shall re- 
turn to this point later on. 

Other interesting examples of this change of views 
are found in two of the most famous living scientists, 
R. Virchow and E. du Bois-Reymond ; the metamor- 
phoses of their fundamental views on psychology can- 
not be overlooked, as both these Berlin biologists have 
played a most important part at Germany's greatest 
university for more than forty years, and have, there- 
fore, directly and indirectly, had a most profound in- 
fluence on the modern mind. Rudolph Virchow, the 
eminent founder of cellular pathology, was a pure mon- 
ist in the best days of his scientific activity, about the 
middle of the century; he passed at that time as one 
of the most distinguished representatives of the newly 
awakened materialism, which appeared in 1855, espe- 
cially through two famous works, almost contempo- 
raneous in appearance Ludwig Biichner's Matter and 
Force and Carl Vogt's Superstition and Science. Vir- 
chow published his general biological views on the vital 
processes in man which he takes to be purely me- 
chanical natural phenomena in a series of distin- 
guished papers in the first volumes of the Archiv fur 
pathologische Anatomie, which he founded. The most 
important of these articles, and the one in which he 
most clearly expresses his monistic views of that 
period, is that on "The Tendencies Towards Unity 
* 93 


in Scientific Medicine" (1849). It was certainly not 
without careful thought, and a conviction of its philo- 
sophic value, that Virchow put this " medical confes- 
sion of faith " at the head of his Collected Essays on 
Scientific Medicine in 1856. He defended in it, clearly 
and definitely, the fundamental principles of monism, 
which I am presenting here with a view to the solu- 
tion of the world-problem ; he vindicated the exclusive 
title of empirical science, of which the only reliable 
sources are sense and brain activity ; he vigorously 
attacked anthropological dualism, the alleged "revela- 
tion," and the transcendental philosophy, with their 
two methods " faith and anthropomorphism . " Above 
all, he emphasized the monistic character of anthro- 
pology, the inseparable connection of spirit and body, 
of force and matter. " I am convinced," he exclaims, 
at the end of his preface, "that I shall never find 
myself compelled to deny the thesis of the unity of 
human nature." Unhappily, this " conviction " proved 
to be a grave error. Twenty- eight years afterwards 
Virchow represented the diametrically opposite view ; 
it is to be found in the famous speech on " The Liberty 
of Science in Modern States/' which he delivered at the 
Scientific Congress at Munich in 1877, and which con- 
tains attacks that 1 have repelled in my Free Science 
and Free Teaching (1878). 

In Emil du Bois-Reymond we find similar contra- 
dictions with regard to the most important and funda- 
mental theses of philosophy. The more completely 
the distinguished orator of the Berlin Academy had 
defended the main principles of the monistic philoso- 
phy, the more he had contributed to the refutation of 
vitalism and the transcendental view of life, so much 
the louder was the triumphant cry of our opponents 



when in 1872, in his famous Ignorabimus-Speech, he 
spoke of consciousness as an insoluble problem, and 
opposed it to the other functions of the brain as a su- 
pernatural phenomenon. I return to the point in the 
tenth chapter. 

The peculiar character of many of the psychic phe- 
nomena, especially of consciousness, necessitates cer- 
tain modifications of our ordinary scientific methods. 
We have, for instance, to associate with the customary 
objective, external observation, the introspective method, 
the subjective, internal observation which scrutinizes 
our own personality in the mirror of consciousness. 
The majority of psychologists have started from this 
" certainty of the ego " : " Cogito ergo sum" as Des- 
cartes said I think, therefore I am. Let us first cast 
a glance at this way of inquiry, and then deal with the 
second, complementary, method. 

By far the greater part of the theories of the soul which 
have been put forward during the last two thousand 
years or more are based on introspective inquiry that 
is, on " self-observation," and on the conclusions which 
we draw from the association and criticism of these 
subjective experiences. Introspection is the only pos- 
sible method of inquiry for an important section of 
psychology, especially for the study of consciousness. 
Hence this cerebral function occupies a special posi- 
tion, and has been a more prolific source of philosophic 
error than any of the others (cf. chap. x.). It is, how- 
ever, most unsatisfactory, and it leads to entirely false 
or incomplete notions, to take this self-observation of 
the mind to be the chief, or, especially, to be the only 
source of mental science, as has happened in the case 
of many and distinguished philosophers. A great 
number of the principal psychic phenomena, particu- 



larly the activity of the senses and speech, can only be 
studied in the same 'way as every other vital function 
of the organism that is, firstly, by a thorough anatom- 
ical study of their organs, and, secondly, by an exact 
physiological analysis of the functions which depend 
on them. In order, however, to complete this external 
study of the mental life, and to supplement the results 
of internal observation, one needs a thorough knowl- 
edge of human anatomy, histology, ontogeny, and 
physiology. Most of our so-called " psychologists " 
have little or no knowledge of these indispensable foun- 
dations of anthropology; they are, therefore, incom- 
petent to pronounce on the character even of their own 
" soul." It must be remembered, too, that the distin- 
guished personality of one of these psychologists usu- 
ally offers a specimen of an educated mind of the high- 
est civilized races ; it is the last link of a long ancestral 
chain, and the innumerable older and inferior links are 
indispensable for its proper understanding. Hence it 
is that most of the psychological literature of the day is 
so much waste paper. The introspective method is cer- 
tainly extremely valuable and indispensable; still it 
needs the constant co-operation and assistance of the 
other methods. 

In proportion as the various branches of the human 
tree of knowledge have developed during the century, 
and the methods of the different sciences have been 
perfected, the desire has grown to make them exact ; 
that is, to make the study of phenomena as purely em- 
pirical as possible, and to formulate the laws that result 
as clearly as the circumstances permit if possible, 
mathematically. The latter is, however, only feasible 
in a small province of human knowledge, especially in 
those sciences in which there is question of measurable 



quantities ; in mathematics, in the first place, and to a 
greater or less extent in astronomy, mechanics, and a 
great part of physics and chemistry. Hence these 
studies are called " exact sciences " in the narrower 
sense. It is, however, productive only of error to call 
all the physical sciences exact, and oppose them to the 
historical, mental, and moral sciences. The greater 
part of physical science can no more be treated as an 
exact science than history can; this is especially true 
of biology and of its subsidiary branch, psychology. 
As psychology is a part of physiology, it must, as a 
general rule, follow the chief methods of that science. 
It must establish the facts of psychic activity by em- 
pirical methods as much as possible, by observation 
and experiment, and it must then gather the laws oi 
the mind by inductive and deductive inferences from 
its observations, and formulate them with the utmost 
distinctness. But, for obvious reasons, it is rarely pos- 
sible to formulate them mathematically. Such a pro- 
cedure is only profitable in one section of the physiology 
of the senses ; it is not practicable in the greater part 
of cerebral physiology. 

One small section of physiology, which seems amen 
able to the " exact " method of investigation, has been 
carefully studied for the last twenty years and raised 
to the position of a separate science under the title of 
psycho-physics. Its founders, the physiologists Theo- 
dor Fechner and Ernst Heinrich Weber, first of all close- 
ly investigated the dependence of sensations on the ex- 
ternal stimuli that act on the organs of sense, and par- 
ticularly the quantitative relation between the strength 
of the stimulus and the intensity of the sensation. They 
found that a certain minimum strength of stimulus is 
requisite for the excitement of a sensation, and that a 



given stimulus must be varied to a definite amount 
before there is any perceptible change in the sensation. 
For the highest sensations (of sight, hearing, and press- 
ure) the law holds good that their variations are pro- 
portionate to the changes in the strength of the stimulus. 
From this empirical " law of Weber " Fechner inferred; 
by mathematical operations, his " fundamental law of 
psycho-physics," according to which the intensity ol 
a sensation increases in arithmetical progression, the 
strength of the stimulus in geometrical progression. 
However, Fechner's law and other psycho-physical laws 
are frequently contested, and their " exactness " is 
called into question. In any case modern psycho- 
physics has fallen far short of the great hopes with 
which it was greeted twenty years ago ; the field of its 
applicability is extremely limited. One important re- 
sult of its work is that it has proved the application of 
physical laws in one, if only a small, branch of the life 
of the " soul " an application which was long ago pos- 
tulated on principle by the materialist psychology for 
the whole province of mental life. In this, as in many 
other branches of physiology, the " exact " method has 
proved inadequate and of little service. It is the ideal 
to aim at everywhere, but it is unattainable in most 
cases. Much more profitable are the comparative and 
genetic methods. 

The striking resemblance of man's psychic activity 
to that of the higher animals especially our nearest 
relatives among the mammals is a familiar fact. 
Most uncivilized races still make no material distinc- 
tion between the two sets of mental processes, as the 
well-known animal fables, the old legends, and the 
idea of the transmigration of souls prove. Even most 
of the philosophers of classical antiquity shared the 


same conviction, and discovered no essential qualita- 
tive difference, but merely a quantitative one, between 
the soul of man and that of the brute. Plato him- 
self, who was the first to draw a fundamental distinc- 
tion between soul and body, made one and the same 
soul (or " idea ") pass through a number of animal and 
human bodies in his theory of metempsychosis. It was 
Christianity, intimately connecting faith in immortal- 
ity with faith in God, that emphasized the essential 
difference of the immortal soul of man from the mortal 
soul of the brute. In the dualistic philosophy the idea 
prevailed principally through the influence of Des- 
cartes (1643) ; he contended that man alone had a true 
" soul," and, consequently, sensation and free will, and 
that the animals were mere automata, or machines, 
without will or sensibility. Ever since the majority of 
psychologists including even Kant have entirely 
neglected the mental life of the brute, and restricted 
psychological research to man: human psychology, 
mainly introspective, dispensed with the fruitful com- 
parative method, and so remained at that lower point 
of view which human morphology took before Cuvier 
raised it to the position of a " philosophic science " by 
the foundation of comparative anatomy. 

Scientific interest in the psychic activity of the brute 
was revived in the second half of the last century, in 
connection with the advance of systematic zoology and 
physiology. A strong impulse was given to it by the 
work of Reimarus : " General observations on the in- 
stincts of animals " (Hamburg, 1760). At the same 
time a deeper scientific investigation had been facili- 
tated by the thorough reform of physiology by Jo- 
hannes Miiller. This distinguished biologist, having 
a comprehensive knowledge of the whole , field of or- 

99 r 


ganic nature, of morphology, and of physiology, in- 
troduced the " exact methods " of observation and ex- 
periment into the whole province of physiology, and, 
with consummate skill, combined them with the com- 
parative methods. He applied them, not only to men- 
tal life in the broader sense (to speech, senses, and brain- 
action), but to all the other phenomena of life. The 
sixth book of his Manual of Human Physiology treats 
specially of the life of the soul, and contains eighty 
pages of important psychological observations. 

During the last forty years a great number of works 
on comparative animal psychology have appeared, 
principally occasioned by the great impulse which 
Darwin gave in 1859 by his work on The Origin of 
Species, and by the application of the idea of evolution 
to the province of psychology. The more impotant 
of these works we owe to Romanes and Sir J. Lubbock, 
in England ; to W. Wundt, L. Biichner, G. Schneider, 
Fritz Schultze, and Karl Groos, in Germany ; to Alfred 
Espinas and E. Jourdan, in France ; and to Tito Vig- 
noli, in Italy. 

In Germany, Wilhelm Wundt, of Leipzig, is consid- 
ered to be the ablest living psychologist ; he has the in- 
estimable advantage over most other philosophers of a 
thorough zoological, anatomical, and physiological ed- 
ucation. Formerly assistant and pupil of Helmholz, 
Wundt had early accustomed himself to follow the ap- 
plication of the laws of physics and chemistry through 
the whole field of physiology, and, consequently, in 
the sense of Johannes Miiller, in psychology, as a sub- 
section of the latter. Starting from this point of view, 
Wundt published his valuable " Lectures on human 
and animal psychology " in 1863. He proved, as he 
himself tells us in the preface, that the theatre of the 


most important psychic processes is in the " unconscious 
soul/' and he affords us "a view of the mechanism 
which, in the unconscious background of the soul, 
manipulates the impressions which arise from the ex- 
ternal stimuli." What seems to me, however, of spe- 
cial importance and value in Wundt's work is that he 
" extends the law of the persistence of force for the 
first time to the psychic world, and makes use of a 
series of facts of electro-physiology by way of demon- 

Thirty years afterwards (1892) Wundt published a 
second, much abridged and entirely modified, edition 
of his work. The important principles of the first edi- 
tion are entirely abandoned in the second, and the mon- 
istic is exchanged for a purely dualistic stand-point. 
Wundt himself says in the preface to the second edition 
that he has emancipated himself from the fundamental 
errors of the first, and that he " learned many years 
ago to consider the work a sin of his youth"; it " weighed 
on him as a kind of crime, from which he longed to free 
himself as soon as possible." In fact, the most impor- 
tant systems of psychology are completely opposed to 
each other in the two editions of Wundt's famous Ob- 
servations. In the first edition he is purely monistic and 
materialistic, in the second edition purely dualistic 
and spiritualistic. In the one psychology is treated 
as a physical science, on the same laws as the whole of 
physiology, of which it is only a part ; thirty years af- 
terwards he finds psychology to be a spiritual science, 
with principles and objects entirely different from those 
of physical science. This conversion is most clearly 
expressed in his principle of psycho-physical parallel- 
'ism, according to which " every psychic event has a 
corresponding physical change " ; but the two are com- 



pletely independent, and are not in any natural causal 
connection. This complete dualism of body and soul, 
of nature and mind, naturally gave the liveliest satis- 
faction to the prevailing school-philosophy, and was 
acclaimed by it as an important advance, especially 
seeing that it came from a distinguished scientist who 
had previously adhered to the opposite system of mon- 
ism. As I myself continue, after more than forty years' 
study, in this " narrow " position, and have not been 
able to free myself from it in spite of all my efforts, I 
must naturally consider the " youthful sin " of the 
young physiologist Wundt to be a correct knowledge 
of nature, and energetically defend it against the an- 
tagonistic view of the old philosopher Wundt. 

This entire change of philosophical principles, which 
we find in Wundt, as we found it in Kant, Virchow, 
Du Bois - Reymond, Karl Ernst Baer, and others, is 
very interesting. In their youth these able and tal- 
ented scientists embrace the whole field of biological 
research in a broad survey, and make strenuous efforts 
to find a unifying, natural basis for their knowledge ; 
in their later years they have found that this is not com- 
pletely attainable, and so they entirely abandon the 
idea. In extenuation of these psychological metamor- 
phoses they can, naturally, plead that in their youth 
they overlooked the difficulties of the great task, and 
misconceived the true goal ; with the maturer judgment 
of age and the accumulation of experience they were 
convinced of their errors, and discovered the true path 
to the source of truth. On the other hand, it is possible 
to think that great scientists approach their task with 
less prejudice and more energy in their earlier years 
that their vision is clearer and their judgment purer; 
the experiences of later years sometimes have the effect, 



not of enriching, but of disturbing, the mind, and with 
old age there comes a gradual decay of the brain, just 
as happens in all other organs. In any case, this 
change of views is in itself an instructive psycho- 
logical fact ; because, like many other forms of 
change of opinion, it shows that the highest psychic 
functions are subject to profound individual changes 
in the course of life, like all the other vital proc- 

For the profitable construction of comparative psy- 
chology it is extremely important not to confine the crit- 
ical comparison to man and the brute in general, but 
to put side by side the innumerable gradations of their 
mental activity. Only thus can we attain a clear knowl- 
edge of the long scale of psychic development which 
runs unbroken from the lowest, unicellular forms of 
life up to the mammals, and to man at their head. But 
even within the limits of our own race such gradations 
are very noticeable, and the ramifications of the " psy- 
chic ancestral tree " are very numerous. The psychic 
difference between the crudest savage of the lowest 
grade and the most perfect specimen of the highest civ- 
ilization is colossal much greater than is commonly 
supposed. By the due appreciation of this fact, espe- 
cially in the latter half of the century, the "Anthropol- 
ogy of the uncivilized races " (Waitz) has received a 
strong support, and comparative ethnography has come 
to be considered extremely important for psychological 
purposes. Unfortunately, the enormous quantity of 
raw material of this science has not yet been treated in 
a satisfactory critical manner. What confused and 
mystic ideas still prevail in this department may be 
seen, for instance, in the Volkergedanke of the famous 
traveller, Adolf Bastian, who, though a prolific writer, 



merely turns out a hopeless mass of uncritical compila- 
tion and confused speculation. 

The most neglected of all psychological methods, 
even up to the present day, is the evolution of the soul ; 
yet this little-frequented path is precisely the one that 
leads us most quickly and securely through the gloomy 
primeval forest of psychological prejudices, dogmas, 
and errors, to a clear insight into many of the chief 
psychic problems. As I did in the other branch of or- 
ganic evolution, I again put before the reader the two 
great branches of the science which I differentiated in 
1866 ontogeny and phylogeny. The ontogeny, or 
embryonic development, of the soul, individual or biontic 
psychogeny, investigates the gradual and hierarchic 
development of the soul in the individual, and seeks to 
learn the laws by which it is controlled. For a great 
part of the life of the mind a good deal has been done 
in this direction for centuries ; rational pedagogy must 
have set itself the task at an early date of the theoret- 
ical study of the gradual development and formative 
capacity of the young mind that was committed to it 
for education and formation. Most pedagogues, how- 
ever, were idealistic or dualistic philosophers, and so 
they went to work with all the prejudices of the spir- 
itualistic psychology. It is only in the last few decades 
that this dogmatic tendency has been largely super- 
seded even in the school by scientific methods ; we now 
find a greater concern to apply the chief laws of evolu- 
tion even in the discussion of the soul of the child. The 
raw material of the child's soul is already qualitatively 
determined by heredity from parents and ancestors; 
education has the noble task of bringing it to a perfect 
maturity by intellectual instruction and moral training 
that is, by adaptation. Wilhelm Preyer was the first 



to lay the foundation of our knowledge of the early 
psychic development in his interesting work on The 
Mind of the Child. Much is still to be done in the 
study of the later stages and metamorphoses of the in- 
dividual soul, and once more the correct, critical ap- 
plication of the biogenetic law is proving a guiding star 
to the scientific mind. 

A new and fertile epoch of higher development 
dawned for psychology and all other biological sciences 
when Charles Darwin applied the principles of evolu- 
tion to them forty years ago. The seventh chapter of 
his epoch-making work on The Origin of Species is 
devoted to instinct. It contains the valuable proof that 
the instincts of animals are subject, like all other vital 
processes, to the general laws of historic development. 
The special instincts of particular species were formed 
by adaptation, and the modifications thus acquired 
were handed on to posterity by heredity ; in their for- 
mation and preservation natural selection plays the 
same part as in the transformation of every other physi- 
ological function. Darwin afterwards developed this 
fundamental thought in a number of works, showing 
that the same laws of "mental evolution" hold good 
throughout the entire organic world, not less in man 
than in the brute, and even in the plant. Hence the 
unity of the organic world, which is revealed by the 
common origin of its members, applies also to the entire 
province of psychic life, from the simplest unicellular 
organism up to man. 

To George Romanes we owe the further development 
of Darwin's psychology and its special application to 
the different sections of psychic activity. Unfortunate- 
ly, his premature decease prevented the completion of 
the great work which was to reconstruct every section 



of comparative psychology on the lines of monistic evo- 
lution. The two volumes of this work which were com- 
pleted are among the most valuable productions of 
psychological literature. For, conformably to the prin- 
ciples of our modern monistic research, his first care 
was to collect and arrange all the important facts which 
have been empirically established in the field of com- 
parative psychology in the course of centuries ; in the 
second place, these facts are tested with an objective 
criticism, and systematically distributed ; finally, such 
rational conclusions are drawn from them on the chief 
general questions of psychology as are in harmony 
with the fundamental principles of modern monism. 
The first volume of Romanes's work bears the title of 
Mental Evolution in the Animal World ; it presents, in 
natural connection, the entire length of the chain of 
psychic evolution in the animal world, from the simplest 
sensations and instincts of the lowest animals to the 
elaborate phenomena of consciousness and reason in 
the highest. It contains also a number of extracts 
from a manuscript which Darwin left "on instinct," 
and a complete collection of all that he wrote in the 
province of psychology. 

The second and more important volume of Romanes's 
work treats of " Mental evolution in man and the origin 
of human faculties." The distinguished psychologist 
gives a convincing proof in it " that the psychological 
barrier between man and the brute has been overcome." 
Man's power of conceptual thought and of abstraction 
has been gradually evolved from the non-conceptual 
stages of thought and ideation in the nearest related 
mammals. Man's highest mental powers reason, 
speech, and conscience have arisen from the lower 
stages of the same faculties in our primate ancestors 

1 06 


(the simiae and prosimiae). Man has no single mental 
faculty which is his exclusive prerogative. His whole 
psychic life differs from that of the nearest related mam- 
mals only in degree, and not in kind ; quantitatively, 
not qualitatively. 

I recommend those of my readers who are interested 
in these momentous questions of psychology to study 
the profound work of Romanes. I am completely at' 
one with him and Darwin in almost all their views and 
convictions. Wherever an apparent discrepancy is 
found between these authors and my earlier produc- 
tions, it is either a case of imperfect expression on my 
part or an unimportant difference in application of 
principle. For the rest, it is characteristic of this 
" science of ideas " that the most eminent philosophers 
hold entirely antagonistic views on its fundamental 


Psychological Unity of Organic Nature Material Basis of the 
Soul : Psychoplasm Scale of Sensation Scale of Movement 
Scale of Reflex Action Simple and Compound Reflex Ac- 
tion Reflex Action and Consciousness Scale of Perception 
Unconscious and Conscious Perception Scale of Memory 
Unconscious and Conscious Memory Association of Per- 
ceptions Instinct Primary and Secondary Instincts Scale 
of Reason Language Emotion and Passion The Will 
Freedom of the Will 

'T'HE great progress which psychology has made, with 
the assistance of evolution, in the latter half of 
the century culminates in the recognition of the psy- 
chological unity of the organic world. Comparative psy- 
chology, in co-operation with the ontogeny and phy- 
logeny of the psyche, has enforced the conviction that 
organic life in all its stages, from the simplest unicel- 
lular protozoon up to man, springs from the same ele- 
mentary forces of nature, from the physiological func- 
tions of sensation and movement. The future task of 
scientific psychology, therefore, is not, as it once was, 
the exclusively subjective and introspective analysis 
of the highly developed mind of a philosopher, but the 
objective, comparative study of the long gradation by 
which man has slowly arisen through a vast series of 
lower animal conditions. This great task of separat- 



ing the different steps in the psychological ladder, and 
proving their unbroken phylogenetic connection, has 
only been seriously attempted during the last ten years, 
especially in the splendid work of Romanes. We must 
confine ourselves here to a brief discussion of a few of 
the general questions which that gradation has sug- 

All the phenomena of the psychic life are, without 
exception, bound up with certain material changes in 
the living substance of the body, the protoplasm. We 
have given to that part of the protoplasm which seems 
to be the indispensable substratum of psychic life the 
name of psychoplasm (the " soul-substance," in the 
monistic sense) ; in other words, we do not attribute 
any peculiar " essence" to it, but we consider the psyche 
to be merely a collective idea of all the psychic functions 
of protoplasm. In this sense the "soul" is merely a 
physiological abstraction like "assimilation" or "gene- 
ration." In man and the higher animals, in accordance 
with the division of labor of the organs and tissues, the 
psychoplasm is a differentiated part of the nervous sys- 
tem, the neuroplasm of the ganglionic cells and their 
'fibres. In the lower animals, however, which have no 
special nerves and organs of sense, and in the plants, 
the psychoplasm has not yet reached an independent 
differentiation. Finally, in the unicellular protists, 
the psychoplasm is identified either with the whole of 
the living protoplasm of the simple cell or with a por- 
tion of it. In all cases, in the lowest as well as the 
highest stages of the psychological hierarchy, a cer- 
tain chemical composition and a certain physical ac- 
tivity of the psychoplasm are indispensable before the 
* soul" can function or act. That is equally true of 
the elementary psychic function of the plasmatic sen- 


sation and movement of the protozoa, and of the com- 
plex functions of the sense-organs and the brain in the 
higher animals and man. The activity of the psycho- 
plasm, which we call the " soul/' is always connected 
with metabolism. 

All living organisms, without exception, are sensi- 
tive ; they are influenced by the condition of their en- 
vironment, and react thereon by certain modifications 
in their own structure. Light and heat, gravity and 
electricity, mechanical processes and chemical action 
in the environment, act as stimuli on the sensitive psy- 
choplasm, and effect changes in its molecular compo- 
sition. We may distinguish the following five chief 
stages of this sensibility : 

I. At the lowest stage of organization the whole 
psychoplasm, as such, is sensitive, and reacts on the 
stimuli from without ; that is the case with the lowest 
protists, with many plants, and with some of the most 
rudimentary animals. 

II. At the second stage very simple and undis- 
criminating sense-organs begin to appear on the sur- 
face of the organism, in the form of protoplasmic fila- 
ments and pigment spots, the forerunners of the nerves 
of touch and the eyes ; these are found in some of the 
higher protists and in many of the lower animals and 

III. At the third stage specific organs of sense, each 
with a peculiar adaptation, have arisen by differentia- 
tion out of these rudimentary processes : there are the 
chemical instruments of smell and taste, and the phys- 
ical organs of touch, temperature, hearing, and sight. 
The " specific energy " of these sense-organs is not an 
original inherent property of theirs, but has been gain- 
ed by functional adaptation and progressive heredity. 



IV. The fourth stage is characterized by the cen- 
tralization or integration of the nervous system, and, 
consequently, of sensation ; by the association of the 
previously isolated or localized sensations presentations 
arise, though they still remain unconscious. That 
is the condition of many both of the lower and the 
higher animals. 

V. Finally, at the fifth stage, the highest psychic 
function, conscious perception, is developed by the mir- 
roring of the sensations in a central part of the nervous 
system, as we find in man and the higher vertebrates, 
and probably in some of the higher invertebrates, not- 
ably the articulata. 

All living organisms without exception have the 
faculty of spontaneous movement, in contradistinction 
to the rigidity and inertia of unorganized substances 
(e.g., crystals) ; in other words, certain changes of place 
of the particles occur in the living psychoplasm from 
internal causes, which have their source in its own 
chemical composition. These active vital movements 
are partly discovered by direct observation and partly 
only known indirectly, by inference from their effects. 
We may distinguish five stages of them. 

I. At the lowest stage of organic life, in the chro- 
macea, and many protophyta and lower metaphyta, 
we perceive only those movements of growth which are 
common to all organisms. They are usually so slow 
that they cannot be directly observed ; they have to be 
inferred from their results from the change in size and 
form of the growing organism. 

II. Many protists, particularly unicellular algae of 
the groups of diatomacea and desmidiacea, accomplish 
a kind of creeping or swimming motion by secretion, by 
ejecting a slimy substance at one side. 



III. Other organisms which float in water for in- 
stance, many of the radiolaria, siphonophora, kteno- 
phora, and others ascend and descend by altering 
their specific gravity, sometimes by osmosis, sometimes 
by the separation or squeezing-out of air. 

IV. Many plants, especially the sensitive plants 
(mimosa) and other papilionacea, effect movements of 
their leaves or other organs by change of pressure 
that is, they alter the strain of the protoplasm, and, 
consequently, its pressure on the enclosing elastic 
walls of the cells. 

V. The most important of all organic movements 
are the phenomena of contraction i.e., changes of form 
at the surface of the organism, which are dependent on 
a twofold displacement of their elements ; they always 
involve two different conditions or phases of motion 
contraction and expansion. Four different forms of 
this plasmatic contraction may be enumerated : 

(a) Amoeboid movement (in rhizopods, blood-cells, 

pigment-cells, etc.). 
(6) A similar flow of protoplasm within enclosed 


(c) Vibratory motion (ciliary movements) in infu- 

soria, spermatozoa, ciliated epithelial cells. 

(d) Muscular movement (in most animals). 

The elementary psychic activity that arises from the 
combination of sensation and movement is called reflex 
(in the widest sense), reflective function, or reflex action. 
The movement no matter what kind it is seems in 
this case to be the immediate result of the stimulus 
which evoked the sensation; it has, on that account, 
been called stimulated motion in its simplest form (in 
the protists). All living protoplasm has this feature 
of irritability. Any physical or chemical change in 



the environment may, in certain circumstances, act as 
a stimulus on the psychoplasm, and elicit or " release " 
a movement. We shall see later on how this impor- 
tant physical concept of " releasing " directly connects 
the simplest organic reflex actions with similar me- 
chanical phenomena of movement in the inorganic 
world (for instance, in the explosion of powder by a 
spark, or of dynamite by a blow). We may distinguish 
the following seven stages in the scale of reflex action : 

I. At the lowest stage of organization, in the lowest 
protists, the stimuli of the outer world (heat, light, 
electricity, etc.) cause in the indifferent protoplasm 
only those indispensable movements of growth and 
nutrition which are common to all organisms, and are 
absolutely necessary for their preservation. That is 
also the case in most of the plants. 

II. In the case of many freely moving protists (es- 
pecially the amoeba, the heliozoon, and the rhizopod) 
the stimuli from without produce on every spot of the 
unprotected surface of the unicellular organism exter- 
nal movements which take the form of changes of shape, 
and sometimes changes of place (amoeboid movement, 
pseudopod formation, the extension and withdrawal of 
what look like feet) ; these indefinite, variable processes 
of the protoplasm are not yet permanent organs. In 
the same way, general organic irritability takes the 
form of indeterminate reflex action in the sensitive 
plants and the lowest metazoa ; in many multicellular 
organisms the stimuli may be conducted from one cell 
to another, as all the cells are connected by fine fibres. 

III. Many protists, especially the more highly de- 
veloped protozoa, produce on their unicellular body 
two little organs of the simplest character an organ 
of touch and an organ of movement. Both these in- 


struments are direct external projections of protoplasm ; 
the stimulus, which alights on the first, is immediately 
conducted to the other by the psychoplasm of the uni- 
cellular body, and causes it to contract. This phenom- 
enon is particularly easy to observe, and even produce 
experimentally, in many of the stationary infusoria 
(for instance, the poteriodendron among the flagellata, 
and the vorticella among the ciliata). The faintest 
stimulus that touches the extremely sensitive hairs, 
or cilia, at the free end of the cells, immediately causes 
a contraction of a thread-like stalk at the other, fixed 
end. This phenomenon is known as a " simple reflex 

IV. These phenomena of the unicellular organism 
of the infusoria lead on to the interesting mechanism 
of the neuro-muscular cells, which we find in the multi- 
cellular body of many of the lower metazoa, especially 
in the cnidaria (polyps and corals) . Each single neuro- 
muscular cell is a " unicellular reflex organ " ; it has 
on its surface a sensitive spot, and a motor muscular 
fibre inside at the opposite end; the latter contracts 
as soon as the former is stimulated. 

V. In other cnidaria, notably in the free swimming 
medusae which are closely related to the stationary 
polyps the simple neuro-muscular cell becomes two 
different cells, connected by a filament; an external 
sense-cell (in the outer skin) and an internal muscular 
cell (under the skin). In this bicellular reflex organ the 
one cell is the rudimentary organ of sensation, the other 
of movement; the connecting bridge of the psycho- 
plasmic filament conducts the stimulus from one to 
the other. 

VI. The most important step in the gradual con- 
struction of the reflex mechanism is the division into 


three cells ; in the place of the simple connecting bridge 
we spoke of there appears a third independent cell, the 
soul-cell, or ganglionic cell ; with it appears also a new 
psychic function, unconscious presentation, which has 
its seat in this cell. The stimulus is first conducted 
from the sensitive cell to this intermediate presentative 
or psychic cell, and then issued from this to the motor 
muscular cell as a mandate of movement. These tri- 
cellular reflex organs are preponderantly developed in 
the great majority of the invertebrates. 

VII. Instead of this arrangement we find in most 
of the vertebrates a quadricellular reflex organ, two dis- 
tinct " soul-cells," instead of one, being inserted be- 
tween the sensitive cell and the motor cell. The ex- 
ternal stimulus, in this case, is first conducted centrip- 
etally to the sensitive cell (the sensible psychic cell), 
from this to the will-cell (the motor psychic cell), and 
from this, finally, to the contractile muscular cell. When 
many such reflex organs combine and new psychic 
cells are interposed we have the intricate reflex mechan- 
ism of man and the higher vertebrates. 

The important distinction which we make, in mor- 
phology and physiology, between unicellular and multi- 
cellular organisms holds good for their elementary 
psychic activity, reflex action. In the unicellular 
protists (both the plasmodomous primitive plants, or 
protophyta, and the plasmophagous primitive animals, 
or protozoa) the whole physical process of reflex action 
takes place in the protoplasm of one single cell ; their 
" cell-soul " seems to be a unifying function of the psy- 
choplasm of which the various phases only begin to 
be seen separately when the differentiation of special 
organs sets in. 

The second stage of psychic activity, compound re- 


flex action, begins with the cenobitic protists (v.g., the 
volvox and the carchesium). The innumerable so- 
cial cells, which make up this cell-community or coeno- 
bium, are always more or less connected, often directly 
connected by filamentous bridges of protoplasm. A 
stimulus that alights on one or more cells of the com- 
munity is communicated to the rest by means of the 
connecting fibres, and may produce a general con- 
traction. This connection is found, also, in the tissues 
of the multicellular animals and plants. It was er- 
roneously believed at one time that the cells of vegetal 
tissue were completely isolated from each other, but 
we have now discovered fine filaments of protoplasm 
throughout, which penetrate the thick membranes of 
the cells, and maintain a material and psychological 
communication between their living plasmic contents. 
That is the explanation of the mimosa: when the 
tread of the passer-by shakes the root of the plant, the 
stimulus is immediately conveyed to all the cells, and 
causes a general contraction of its tender leaves and a 
drooping of the stems. 

An important and universal feature of all reflex phe- 
nomena is the absence of consciousness. For reasons 
which we shall give in the tenth chapter we only ad- 
mit the presence of consciousness in man and the 
higher animals, not in plants, the lower animals, and 
the protists; consequently all stimulated movements 
in the latter must be regarded as reflex that is, all 
movements which are not spontaneous, not the out- 
come of internal causes (impulsive and automatic 
movements).* It is different with the higher animals 
which have developed a centralized nervous system and 

* Cf . Max Verworn, Psychophysiologische Protisten-Studien, pp. 

135, 140- 



elaborate sense-organs. In these cases consciousness 
has been gradually evolved from the psychic reflex ac- 
tivity, and now conscious, voluntary action appears, in 
opposition to the still continuing reflex action below. 
However, we must distinguish two different processes, 
as we did in the question of instinct primary and sec- 
ondary reflex action. Primary reflex actions are those 
which have never reached the stage of consciousness in 
phyletic development, and thus preserve the primitive 
character (by heredity from lower animal forms). Sec- 
ondary reflex actions are those which were conscious, 
voluntary actions in our ancestors, but which afterwards 
became unconscious from habit or the lapse of conscious- 
ness. It is impossible to draw a hard and fast line in 
such cases between conscious and unconscious psychic 

Older psychologists (Herbart, for instance) consid- 
ered " presentation " to be the fundamental psychic phe- 
nomenon, from which all the others are derived. Mod- 
ern comparative psychology endorses this view in so 
far as it relates to the idea of unconscious presentation ; 
but it considers conscious presentation to be a secondary 
phenomenon of mental life, which is entirely wanting 
in plants and the lower animals, and is only developed 
in the higher animals. Among the many contradictory 
definitions which psychologists have given of " presen- 
tation/' we think the best is that which makes it consist 
in an internal picture of the external object which is 
given us in sensation an " idea/' in the broader sense. 
We may distinguish the following four stages in the 
rising scale of presentative function : 

I. Cellular presentation. At the lowest stages we 
find presentation to be a general physiological property 
of psychoplasm ; even in the simplest unicellular protist 



sensations may leave a permanent trace in the psycho- 
plasm, and these may be reproduced by memory. In 
more than four thousand kinds of radiolaria, which I 
have described, every single species is distinguished by 
special, hereditary skeletal structure. The construc- 
tion of this specific, and often highly elaborate, skeleton 
by a cell of the simplest description (generally globular) 
is only intelligible when we attribute the faculty of pres- 
entation, and, indeed, of a special reproduction of the 
plastic " feeling of distance," to the constructive proto- 
plasm as I have pointed out in my Psychology of the 

II. Histionic presentation. In the ccenobia or cell- 
colonies of the social protists, and still better in the 
tissues of plants and lower, nerveless animals (sponges, 
polyps, etc.), we find the second stage of unconscious 
presentation, which consists of the common psychic ac- 
tivity of a number of closely connected cells. If a single 
stimulus may, instead of simply spending itself in the 
reflex movement of an organ (the leaf of a plant, for in- 
stance, or the arm of a polyp), leave a permanent im- 
pression, which can be spontaneously reproduced later 
on, we are bound to assume, in explaining the phenom- 
enon, a histionic presentation, dependent on the psycho- 
plasm of the associated tissue-cells. 

III. Unconscious presentation in the ganglionic cells. 
This third and higher stage of presentation is the 
commonest form the function takes in the animal world ; 
it seems to be a localization of presentation in definite 
" soul-cells. " In its simplest form it appears at the sixth 
stage of reflex action, when the tricellular reflex organ 
arises : the seat of presentation is then the intermediate 

*E. Haeckel, * General Natural History of the Radiolaria "; 



psychic cell, which is interposed between the sensitive 
cell and the muscular cell. With the increasing devel- 
opment of the animal nervous system and its progres- 
sive differentiation and integration, this unconscious 
presentation also rises to higher stages. 

IV. Conscious presentation in the cerebral cells. 
With the highest stage of development of the animal 
organization consciousness arises, as a special function 
of a certain central organ of the nervous system. As 
the presentations are conscious, and as special parts of 
the brain arise for the association of these conscious 
presentations, the organism is qualified for those highest 
psychic functions which we call thought and reflection, 
intellect and reason. Although the tracing of the phy- 
letic barrier between the older, unconscious, and the 
younger, conscious, presentation is extremely difficult, 
we can affirm, with some degree of probability, that the 
evolution of the latter from the former was polyphyletic ; 
because we find conscious and rational thought, not 
only in the highest forms of the vertebrate stem (man, 
mammals, birds, and a part of the lower vertebrates), 
but also in the most highly developed representatives of 
other animal groups (ants and other insects, spiders and 
the higher crabs among the articulata, cephalopods 
among the mollusca). 

The evolutionary scale of memory is closely connected 
with that of presentation; this extremely important 
function of the psychoplasm the condition of all fur- 
ther psychic development consists essentially in the 
reproduction of presentations. The impressions in the 
bioplasm, which the stimulus produced as sensations, 
and which became presentations in remaining, are re- 
vived by memory ; they pass from potentiality to actu- 
ality. The latent potential energy of the psychoplasm 


is transformed into kinetic energy. We may distin- 
guish four stages in the upward development of mem- 
ory, corresponding to the four stages of presentation. 

I. Cellular memory. Thirty years ago Ewald He- 
ring showed " memory to be a general property of organ- 
ized matter " in a thoughtful work, and indicated the 
great significance of this function, "to which we owe 
almost all that we are and have." Six years later, in 
my work on The Perigenesis of the Plastidule, or the Un- 
dulatory Origin of the Parts of Life : an Experiment in 
the Mechanical Explanation of Elementary Evolutionary 
Processes, I developed these ideas, and endeavored to 
base them on the principles of evolution. I have at- 
tempted to show in that work that unconscious mem- 
ory is a universal and very important function of all 
plastidules ; that is, of those hypothetical molecules, or 
groups of molecules, which Naegeli has called micellae, 
others bioplasts, and so forth. Only living plastidules, 
as individual molecules of the active protoplasm, are re- 
productive, and so gifted with memory; that is the 
chief difference between the organic and inorganic 
worlds. It might be stated thus : " Heredity is the 
memory of the plastidule, while variability is its compre- 
hension." The elementary memory of the unicellular 
protist is made up of the molecular memory of the 
plastidules or micellae, of which its living cell-body is 
constructed. As regards the extraordinary perform- 
ances of unconscious memory in these unicellular pro- 
tists, nothing could be more instructive than the infi- 
nitely varied and regular formation of their defensive 
apparatus, their shells and skeletons ; in particular, 
the diatomes and cosmaria among the protophytes, and 
the radiolaria and thalamophora among the protozoa, 
afford an abundance of most interesting illustrations. 



In many thousand species of these protists the specific 
form which is inherited is relatively constant, and proves 
the fidelity of their unconscious cellular memory. 

II. Histionic memory. Equally interesting exam- 
ples of the second stage of memory, the unconscious 
memory of tissues, are found in the heredity of the in- 
dividual organs of plants and the lower, nerveless ani- 
mals (sponges, etc.). This second stage seems to be a 
reproduction of the histionic presentations, that associa- 
tion of cellular presentations which sets in with the 
formation of coenobia in the social protists. 

III. In the same way we must regard the third stage, 
the unconscious memory of those animals which have 
a nervous system, as a reproduction of the correspond- 
ing * unconscious presentations " which are stored up 
in certain ganglionic cells. In most of the lower ani- 
mals all memory is unconscious. Moreover, even in 
man and the higher animals, to whom we must ascribe 
consciousness, the daily acts of unconscious memory 
are much more numerous and varied than those of the 
conscious faculty; we shall easily convince ourselves 
of that if we make an impartial study of a thousand 
unconscious acts we perform daily out of habit, and 
without thinking of them, in walking, speaking, writ- 
ing, eating, and so forth. 

IV. Conscious memory, which is the work of cer- 
tain brain-cells in man and the higher animals, is an 
" internal mirroring " of very late development, the 
highest outcome of the same psychic reproduction of 
presentations which were mere unconscious processes 
in the ganglionic cells of our lower animal ancestors. 

The concatenation of presentations usually called 
the association of ideas also runs through a long 
scale, from the lowest to the highest stages. This, 



too, is originally and predominantly unconscious (" in- 
stinct ") ; only in the higher classes of animals does it 
gradually become conscious (" reason "). The psychic 
results of this " association of ideas" are extremely 
varied ; still, a very long, unbroken line of gradual de- 
velopment connects the simplest unconscious associa- 
tion of the lowest protist with the elaborate conscious 
chain of ideas of the civilized man. The unity of con- 
sciousness in man is given as its highest consequence 
(Hume, Condillac). All higher mental activity be- 
comes more perfect in proportion as the normal associa- 
tion extends to more numerous presentations, and in 
proportion to the order which is imposed on them by 
the "criticism of pure reason." In dreams, where this 
criticism is absent, the association of the reproduced 
impressions often takes the wildest forms. Even in 
the work of the poetic imagination, which constructs 
new groups of images by varying the association of 
the impressions received, and in hallucinations, etc., 
they are often most unnaturally arranged, and seem 
to the prosaic observer to be perfectly irrational. This 
is especially true of supernatural " forms of belief," the 
apparitions of spiritism, and the fantastic notions of 
the transcendental dualist philosophy ; though it is 
precisely these abnormal associations of " faith " and 
of " revelation " that have often been deemed the great- 
est treasures of the human mind (cf. chap. xvi.). 

The antiquated psychology of the Middle Ages 
(which, however, still numbers many adherents) con- 
sidered the mental life of man and that of the brute to 
be two entirely different phenomena ; the one it attrib- 
uted to " reason," the other to " instinct." In harmony 
with the traditional story of creation, it was assumed 
that each animal species had received a definite, un- 



conscious psychic force from the Creator at its forma- 
tion, and that this instinct of each species was just as 
unchangeable as its bodily structure. Lamarck proved 
the untenableness of this error in 1809 by establishing 
the theory of Descent, and Darwin completely demol- 
ished it in 1859. He proved the following important 
theses with the aid of his theory of selection : 

1. The instincts of species show individual differ- 
ences, and are just as subject to modification under the 
law of adaptation as the morphological features of their 
bodily structure. 

2. These modifications (generally arising from a 
change of habits) are partly transmitted to offspring 
by heredity, and thus accumulate and are accentuated 
in the course of generations. 

3. Selection, both artificial and natural, singles out 
certain of these inherited modifications of the psychic 
activity ; it preserves the most useful and rejects the 
least adaptive. 

4 The divergence of psychic character which thus 
arises leads, in the course of generations, to the forma- 
tion of new instincts, just as the divergence of morpho- 
logical character gives rise to new species. 

Darwin s theory of instinct is now accepted by most 
biologists; Romanes has treated it so ably, and so 
greatly expanded it in his distinguished work on Mental 
Evolution in the Animal World, that I need merely re- 
fer to it here. I will only venture the brief statement 
that, in my opinion, there are instincts in all organisms 
in all the protists and plants as well as in all the ani- 
mals and in man ; though in the latter they tend to dis- 
appear in proportion as reason makes progress at their 

The two chief classes of instincts to be differentiated 


are the primary and secondary. Primary instincts are 
the common lower impulses which are unconscious and 
inherent in the psychoplasm from the commencement 
of organic life; especially the impulses to self-preser- 
vation (by defence and maintenance) and to the preser- 
vation of the species (by generation and the care of the 
young). Both these fundamental instincts of organic 
life, hunger and love, sprang up originally in perfect 
unconsciousness, without any co-operation of the intel- 
lect or reason. It is otherwise with the secondary in- 
stincts. These were due originally to an intelligent 
adaptation, to rational thought and resolution, and to 
purposive conscious action. Gradually, however, they 
became so automatic that this "other nature * acted 
unconsciously, and, even through the action of hered- 
ity, seemed to be * innate * in subsequent generations. 
The consciousness and deliberation which originally 
accompanied these particular instincts of the higher 
animals and man have died away in the course of the 
life of the plastidules (as in " abridged heredity "). 
The unconscious purposive actions of the higher ani- 
mals (for instance, their mechanical instincts) thus 
come to appear in the light of innate impulses. We 
have to explain in the same way the origin of the " h 
priori ideas " of man ; they were originally formed 
empirically by his predecessors.* 

In the superficial psychological treatises which ig- 
nore the mental activity of animals and attribute to 
man only a " true soul," we find him credited also with 
the exclusive possession of reason and consciousness. 
This is another trivial error (still to be found in many 
a manual, nevertheless) which the comparative psy- 

* Vide Natural History of Creation, E. Haeckel. 


chology of the last forty years has entirely dissipated. 
The higher vertebrates (especially those mammals 
which are most nearly related to man) have just as 
good a title to "reason" as man himself, and within 
the limits of the animal world there is the same long 
chain of the gradual development of reason as in the 
case of humanity. The difference between the reason 
of a Goethe, a Kant, a Lamarck, or a Darwin, and that 
of the lowest savage, a Veddah, an Akka, a native 
Australian, or a Patagonian, is much greater than the 
graduated difference between the reason of the latter 
and that of the most " rational" mammals, the anthro- 
poid apes, or even the papiomorpha, the dog, or the 
elephant. This important thesis has been convinc- 
ingly proved by the thoroughly critical comparative 
work of Romanes and others. We shall not, there- 
fore, attempt to cover that ground here, nor to enlarge 
on the distinction between the reason and the intel- 
lect; as to the meaning and limits of these concepts 
philosophic experts give the most contradictory defi- 
nitions, as they do on so many other fundamental ques- 
tions of psychology. In general it may be said that 
the process of the formation of concepts, which is com- 
mon to both these cerebral functions, is confined to the 
narrower circle of concrete, proximate associations in 
the intellect, but reaches out to the wider circle of ab- 
stract, more comprehensive groups of associations in 
the work of reason. In the long gradation which con- 
nects the reflex actions and the instincts of the lower 
animals with the reason of the highest, intellect pre- 
cedes the latter. And there is the fact, of great im- 
portance to our whole psychological treatise, that even 
these highest of our mental faculties are just as much 
subject to the laws of heredity and adaptation as are 
10 125 


their respective organs; Flechsig pointed out in 1894 
that the " organs of thought/' in man and the higher 
mammals, are those parts of the cortex of the brain 
which lie between the four inner sense-centres (cf . chap- 
ters x. and xi.). 

The higher grade of development of ideas, of intellect 
and reason, which raises man so much above the brute, 
is intimately connected with the rise of language. Still 
here also we have to recognize a long chain of evolu- 
tion which stretches unbroken from the lowest to the 
highest stages. Speech is no more an exclusive pre- 
rogative of man than reason. In the wider sense, it is 
a common feature of all the higher gregarious animals, 
at least of all the articulata and the vertebrates, which 
live in communities or herds ; they need it for the pur- 
pose of understanding each other and communicating 
their impressions. This is effected either by touch 
or by signs, or by sounds having a definite meaning. 
The song of the bird or of the anthropoid ape (hylo- 
bates), the bark of the dog, the neigh of the horse, the 
chirp of the cricket, the cry of the cicada, are all speci- 
mens of animal speech. Only in man, however, has 
that articulate conceptual speech developed which has 
enabled his reason to attain such high achievements. 
Comparative philology, one of the most interesting 
sciences that has arisen during the century, has shown 
that the numerous elaborate languages of the different 
nations have been slowly and gradually evolved from 
a few simple primitive tongues (Wilhelm Humboldt, 
Bopp, Schleicher, Steinthal, and others). August 
Schleicher, of Jena, in particular, has proved that the 
historical development of language takes place under 
the same phylogenetic laws as the evolution of other 
physiological faculties and their organs. Romanes 



(1893) has expanded this proof, and amply demon- 
strated that human speech, also, differs from that of 
the brute only in degree of development, not in essence 
and kind. 

The important group of psychic activities which we 
embrace under the name of "emotion" plays a con- 
spicuous part both in theoretical and practical psychol- 
ogy. From our point of view they have a peculiar im- 
portance from the fact that we dearly see in them the 
direct connection of cerebral functions with other phys- 
iological functions (the beat of the heart, sense - action, 
muscular movement, etc.) ; they, therefore, prove the 
unnatural and untenable character of the philosophy 
which would essentially dissociate psychology from 
physiology. All the external expressions of emotional 
life which we find in man are also present in the higher 
animals (especially in the anthropoid ape and the 
dog) ; however varied their development may be, they 
are all derived from the two elementary functions of 
the psyche, sensation and motion, and from their com- 
bination in reflex action and presentation. To the 
province of sensation, in a wide sense, we must attrib- 
ute the feeling of like and dislike which determines the 
emotion ; while the corresponding desire and aversion 
(love and hatred), the effort to attain what is liked and 
avoid what is disliked, belong to the category of move- 
ment. " Attraction " and " repulsion " seem to be the 
sources of will, that momentous element of the soul 
which determines the character of the individual. The 
passions, which play so important a part in the psychic 
life of man, are but intensifications of emotion. Ro- 
manes has recently shown that these also are common 
to man and the brute. Even at the lowest stage of or- 
ganic life we find in all the protists those elementary 



feelings of like and dislike, revealing themselves in 
what are called their tropisms, in the striving after light 
and darkness, heat or cold, and in their different rela- 
tions to positive and negative electricity. On the other 
hand, we find at the highest stage of psychic life, in 
civilized man, those finer shades of emotion, of delight 
and disgust, of love and hatred, which are the main- 
springs of civilization and the inexhaustible sources 
of poetry. Yet a connecting chain of all conceivable 
gradations unites the most primitive elements of feel- 
ing in the psychoplasm of the unicellular protist with 
the highest forms of passion that rule in the ganglionic 
cells of the cortex of the human brain. That the latter 
are absolutely amenable to physical laws was proved 
long ago by the great Spinoza in his famous Statics 
of Emotion. 

The notion of will has as many different meanings 
and definitions as most other psychological notions 
presentation, soul, mind, and so forth. Sometimes will 
is taken in the widest sense as a cosmic attribute, as 
in the " World as will and presentation " of Schopen- 
hauer; sometimes it is taken in its narrowest sense as 
an anthropological attribute, the exclusive prerogative 
of man as Descartes taught, for instance, who consid- 
ered the brute to be a mere machine, without will or sen- 
sation. In the ordinary use of the term, will is derived 
from the phenomenon of voluntary movement, and is 
thus regarded as a psychic attribute of most animals. 
But when we examine the will in the light of compara- 
tive physiology and evolution, we find as we do in the 
case of sensation that it is a universal property of liv- 
ing psychoplasm. The automatic and the reflex move- 
ments which we observe everywhere, even in the uni- 
cellular protists, seem to be the outcome of inclinations 



which are inseparably connected with the very idea of 
life. Even in the plants and lowest animals these in- 
clinations, or tropisms, seem to be the joint outcome of 
the inclinations of all the combined individual cells. 

But when the " tricellular reflex organ " arises (page 
115), and a third independent cell the " psychic/' or 
" ganglionic," cell is interposed between the sense-cell 
and the motor cell, we have an independent elementary 
organ of will. In the lower animals, however, this will 
remains unconscious. It is only when consciousness 
arises in the higher animals, as the subjective mirror 
of the objective, though internal, processes in the neuro- 
plasm of the psychic cells, that the will reaches that 
highest stage which likens it in character to the human 
will, and which, in the case of man, assumes in com- 
mon parlance the predicate of " liberty. " Its free do- 
minion and action become more and more deceptive 
as the muscular system and the sense-organs develop 
with a free and rapid locomotion, entailing a correlative 
evolution of the brain and the organs of thought. 

The question of the liberty of the will is the one which 
has more than any other cosmic problem occupied the 
time of thoughtful humanity, the more so that in this 
case the great philosophic interest of the question was 
enhanced by the association of most momentous con- 
sequences for practical philosophy for ethics, educa- 
tion, law, and so forth. Emil du Bois-Reymond, who 
treats it as the seventh and last of his " seven cosmic 
problems," rightly says of the question : " Affecting 
everybody, apparently accessible to everybody, inti- 
mately involved in the fundamental conditions of hu- 
man society, vitally connected with religious belief, this 
question has been of immeasurable importance in the 
history of civilization. There is probably no other ob- 



ject of thought on which the modern library contains so 
many dusty folios that will never again be opened." 
The importance of the question is also seen in the fact 
that Kant put it in the same category with the questions 
of the immortality of the soul and belief in God. He 
called these three great questions the indispensable 
" postulates of practical reason/' though he had already 
clearly shown them to have no reality whatever in the 
light of pure reason. 

The most remarkable fact in connection with this 
fierce and confused struggle over the freedom of the 
will is, perhaps, that it has been theoretically rejected, 
not only by the greatest critical philosophers, but even 
by their extreme opponents, and yet it is still affirmed 
to be self-evident by the majority of people. Some of 
the first teachers of the Christian Churches such as 
St. Augustine and Calvin rejected the freedom of the 
will as decisively as the famous leaders of pure ma- 
terialism, Holbach in the eighteenth and Buchner in 
the nineteenth century. Christian theologians deny it, 
because it is irreconcilable with their belief in the om- 
nipotence of God and in predestination. God, omnip- 
otent and omniscient, saw and willed all things from 
eternity he must, consequently, have predetermined 
the conduct of man. If man, with his free will, were 
to act otherwise than God had ordained, God would not 
be all-mighty and all-knowing. In the same sense 
Leibnitz, too, was an unconditional determinist. The 
monistic scientists of the last century, especially La- 
place, defended determinism as a consequence of their 
mechanical view of life. 

The great struggle between the determinist and the 
indeterminist, between the opponent and the sustainer 
of the freedom of the will, has ended to-day, after more 



than two thousand years, completely in favor of the 
determinist. The human will has no more freedom 
than that of the higher animals, from which it differs 
only in degree, not in kind. In the last century the 
dogma of liberty was fought with general philosophic 
and cosmological arguments. The nineteenth century 
has given us very different weapons for its definitive 
destruction the powerful weapons which we find in 
the arsenal of comparative physiology and evolution. 
We now know that each act of the will is as fatally 
determined by the organization of the individual and 
as dependent on the momentary condition of his envi- 
ronment as every other psychic activity. The charac- 
ter of the inclination was determined long ago by 
heredity from parents and ancestors ; the determina- 
tion to each particular act is an instance of adaptation 
to the circumstances of the moment wherein the 
strongest motive prevails, according to the laws which 
govern the statics of emotion. Ontogeny teaches us 
to understand the evolution of the will in the individu- 
al child. Phylogeny reveals to us the historical de- 
velopment of the will within the ranks of our verte- 
brate ancestors. 


Importance of Ontogeny to Psychology Development of the Child- 
Soul Commencement of Existence of the Individual Soul 
The Storing of the Soul Mythology of the Origin of the Soul 
Physiology of the Origin of the Soul Elementary Processes 
in Conception Coalescence of the Ovum and the Spermato- 
zoon Cell-Love Heredity of the Soul from Parents and An- 
cestors Its Physiological Nature as the Mechanics of the 
Protoplasm Blending of Souls (Psychic Amphigony) Re- 
version, Psychological Atavism The Biogenetic Law in Psy- 
chology Palingenetic Repetition and Cenogenetic Modifica- 
tion Embryonic and Post-Embryonic Psychogeny. 

THE human soul whatever we may hold as to 
its nature undergoes a continual development 
throughout the life of the individual. This ontogenetic 
fact is of fundamental importance in our monistic psy- 
chology, though the " professional" psychologists pay 
little or no attention to it. Since the embryology of the 
individual is, on Baer's principle and in accordance 
with the universal belief of modern biologists the 
"true torch-bearer for all research into the organic 
body/' it will afford us a reliable light on the momen- 
tous problems of its psychic activity. 

Although, however, this " embryology of the soul " is 
so important and interesting, it has hitherto met with 
the consideration it deserves only within a very narrow 
circle. Until recently teachers were almost the only 



ones to occupy themselves with a part of the problem ; 
since their avocation compelled them to assist and su- 
pervise the formation of the psychic activity in the child, 
they were bound to take a theoretical interest, also, in 
the psychogenetic facts that came under their notice. 
However, these teachers, for the most part, both in re- 
cent and in earlier times, were dominated by the cur- 
rent dualistic psychology in so far as they reflected at 
all; and they were totally ignorant of the important 
facts of comparative psychology, and unacquainted 
with the structure and function of the brain. More- 
over, their observations only extended to children in 
their school-days, or in the years immediately preced- 
ing. The remarkable phenomena which the individ- 
ual psychogeny of the child offers in its earliest years, 
and which are the joy and admiration of all thoughtful 
parents, were scarcely ever made the subject of serious 
scientific research. Wilhelm Preyer was the pioneer 
of this study in his interesting work on The Mind of the 
Child (1881). To obtain a perfectly clear knowledge of 
the matter, however, we must go further back still; 
we must commence at the first appearance of the soul 
in the impregnated ovum. 

The origin of the human individual body and soul 
was still wrapped in complete mystery at the begin- 
ning of the nineteenth century. Caspar Friedrich Wolff 
had, it is true, discovered the true character of embry- 
onic development in 1759, in his theoria generationis, 
and proved with the confidence of a critical observer 
that there is a true epigenesis i.e., a series of very re- 
markable formative processes in the evolution of the 
foetus from the simple ovum. But the physiologists of 
the time, with the famous Albert Haller at their head, 
flatly refused to entertain these empirical truths, which 


may be directly proved by microscopic observation, and 
clung to the old dogma of " pref ormation. " This theory 
assumed that in the human ovum and in the egg of 
all other animals the organism was already present, 
or " preformed," in all its parts ; the " evolution " of 
the embryo consisted literally in an " unfolding " (evo- 
lutio) of the folded organs. One curious consequence 
of this error was the theory of scatulation, which we 
have mentioned on p. 55 ; since the ovary had to be 
admitted to be present in the embryo of the woman, it 
was also necessary to suppose that the germs of the next 
generation were already formed in it, and so on in in- 
finitum. Opposed to this dogma of the " Ovulists " 
was the equally erroneous notion of the "Animalcu- 
lists"; the latter held that the germ was not really in 
the female ovum, but in the paternal element, and that 
the store of succeeding generations was to be sought in 
the spermatozoa. 

Leibnitz consistently applied this theory of scatula- 
tion to the human soul ; he denied that either soul or 
body had a real development (epigenesis) , and said in 
his Theodicy : " Thus I consider that the souls which 
are destined one day to become human exist in the 
seed, like those of other species ; that they have existed 
in our ancestors as far back as Adam that is, since the 
beginning of the world in the forms of organized bod- 
ies." Similar notions prevailed in biology and philos- 
ophy until the third decade of the present century, when 
the reform of embryology by Baer gave them their 
death blow. In the province of psychology, however, 
they still find many adherents ; they form one group of 
the many curious mystical ideas which give us a living 
illustration of the ontogeny of the soul. 

The more accurate knowledge which we have recent- 
J 34 


ly obtained, through comparative ethnology, of the va- 
rious forms of myths of ancient and modern uncivilized 
races, is also of great interest in psychogeny. Still, it 
would take us too far from our purpose if we were to 
enter into it with any fulness here ; we must refer the 
reader to Adalbert Svoboda's excellent work on Forms 
of Faith (1897). In respect of their scientific and poet- 
ical contents, we may arrange all pertinent psychoge- 
netic myths in the following five groups : 

I. The myth of transmigration. The soul lived for- 
merly in the body of another animal, and passed from 
this into a human body. The Egyptian priests, for in- 
stance, taught that the human soul wandered through 
all the species of animals after the death of the body, 
returning to a human frame after three thousand years 
of transmigration. 

II. The myth of the in-planting of the soul. The 
soul existed independently in another place a psycho- 
genetic store, as it were (in a kind of embryonic slumber 
or latent life) ; it was taken out by a bird (sometimes 
represented as an eagle, generally as a white stork), 
and implanted in the human body. 

III. The myth of the creation of the soul. God cre- 
ates the souls, and keeps them stored sometimes in a 
pond (living in the form of plankton), according to other 
myths in a tree (where they are conceived as the fruit 

, of a phanerogam) ; the Creator takes them from the 
pond or tree, and inserts them in the human germ dur- 
ing the act of conception. 

IV. The myth of the scatulation of the soul (the the- 
ory of Leibnitz which we have given above). 

V. The myth of the division of the soul (the theory 
of Rudolph Wagner [1855] and of other physiologists). 
In the act of procreation a portion is detached from 


both the (immaterial) souls of the parents; the ma- 
ternal contribution passes in the ovum, the paternal 
in the spermatozoa; when these two germinal cells 
coalesce, the two psychic fragments that accompany 
them also combine to form a new (immaterial) soul. 

Although the poetic fancies we have mentioned as 
to the origin of the individual human soul are still wide- 
ly accepted, their purely mythological character is now 
firmly established. The deeply interesting and re- 
markable research which has been made in the course 
of the last twenty-five years into the more minute proc- 
esses of the impregnation and germination of the ovum 
has made it clear that these mysterious phenomena 
belong entirely to the province of cellular physiology 
(cf. p. 48). Both the female element, the ovum, and 
the male fertilizing body, the sperma or spermatozoa, 
are simple cells. These living cells possess a certain 
sum of physiological properties to which we give the 
title of the " cell-soul," just as we do in the permanently 
unicellular protist (see p. 48). Both germinal cells 
have the faculty of movement and sensation. The 
young ovum, or egg-cell, moves after the manner of an 
amoeba; the minute spermatozoa, of which there are 
millions in every drop of the seminal fluid, are ciliated 
cells, and swim about as freely in the sperm, by means 
of their lashes or cilia, as the ordinary ciliated infuso- 
ria (the flagellata). 

When the two cells meet as a result of copulation, 
or when they are brought into contact through arti- 
ficial fertilization (in the fishes, for instance), they at- 
tract each other and become firmly attached. The 
main cause of this cellular attraction is a chemical sen- 
sitive action of the protoplasm, allied to smell or taste, 
which we call " erotic chemicotropism " ; it may also 



be correctly (both in the chemical and the romantic 
sense) termed " cellular affinity " or " sexual cell-love." 
A number of the ciliated cells in the sperm swim rap- 
idly towards the stationary egg-cell and seek to pene- 
trate into it. As Hertwig showed in 1 875, as a rule only 
one of the suitors is fortunate enough to reach the de- 
sired goal. As soon as this favored spermatozoon has 
pierced into the body of the ovum with its head (the 
nucleus of the cell), a thin mucous layer is detached 
from the ovum which prevents the further entrance of 
spermatozoa. The formation of this protective mem- 
brane was only prevented when Hertwig kept the ovum 
stiff with cold by lowering the temperature, or benumbed 
it with narcotics (chloroform, morphia, nicotine, etc.) ; 
then there was " super-impregnation " or " poly-spermy " 
a number of sperm-threads pierced into the body of 
the unconscious ovum. This remarkable fact proved 
that there is a low degree of "cellular instinct" (or, at 
least, of specific, lively sensation) in the sexual cells 
just as effectively as do the important phenomena that 
immediately follow in their interior. Both nuclei 
that of the ovum and of the spermatozoon attract each 
other, approach, and, on contact, completely fuse to- 
gether. Thus from the impregnated ovum arises the 
important new cell which we call the " stem-cell " (cy- 
tula], from the repeated segmentation of which the 
whole polycellular organism is evolved. 

The psychological information which is afforded by 
these remarkable facts of impregnation, which have 
only been properly observed during the last twenty- 
five years, is supremely important; its vast signifi- 
cance has hitherto been very far from appreciated. We 
shall condense the main conclusions of research in the 
following five theses: 


I. Each human individual, like every other higher 
animal, is a single simple cell at the commencement 
of his existence. 

II. This "stem-cell" (cytula) is formed in the same 
manner in all cases that is, by the blending or copu- 
lation of two separate cells of diverse origin, the female 
ovum and the male spermatozoon. 

III. Each of these sexual cells has its own " cell- 
soul" that is, each is distinguished by a peculiar 
form of sensation and movement. 

IV. At the moment of conception or impregnation, 
not only the protoplasm and the nuclei of the two sex- 
ual cells coalesce, but also their "cell-souls"; in other 
words, the potential energies which are latent in both, 
and inseparable from the matter of the protoplasm, 
unite for the formation of a new potential energy, the 
" germ-soul " of the newly constructed stem-cell. 

V. Consequently each personality owes his bodily 
and spiritual qualities to both parents; by heredity 
the nucleus of the ovum contributes a portion of the 
maternal features, while the nucleus of the sperma- 
tozoon brings a part of the father's characteristics. 

By these empirical facts of conception, moreover, 
the further fact of extreme importance is established, 
that every man, like every other animal, has a begin- 
ning of existence ; the complete copulation of the two 
sexual cell-nuclei marks the precise moment when not 
only the body, but also the " soul," of the new stem- 
cell makes its appearance. This fact suffices of itself 
to destroy the myth of the immortality of the soul, to 
which we shall return later on. It suffices, too, for 
the destruction of the still prevalent superstition that 
man owes his personal existence to the favor of God. 
Its origin is rather to be attributed solely to the " eros " 


of his parents, to that powerful impulse that is common 
to all polycellular animals and plants, and leads to 
their nuptial union. But the essential point in this 
physiological process is not the " embrace/' as was 
formerly supposed, or the amorousness connected there- 
with ; it is simply the introduction of the spermatozoa 
into the vagina. This is the sole means, in the land- 
dwelling animals, by which the fertilizing element can 
reach the released ova (which usually takes place in 
the uterus in man). In the case of the lower aquatic 
animals (fishes, mussels, medusae, etc.) the mature 
sexual elements on both sides are simply discharged 
into the water, and their union is let to chance; they 
have no real copulation, and so they show none of those 
higher psychic " erotic " functions which play so con- 
spicuous a part in the life of the higher animals. Hence 
it is, also, that all the lower, non - copulating animals 
are wanting in those interesting organs which Darwin 
has called " secondary sexual characters," and which 
are the outcome of sexual selection : such are the beard 
of man, the antlers of the stag, the beautiful plumage 
of the bird of paradise and of so many other birds, to- 
gether with other distinctions of the male which are 
absent in the female. 

Among the above theses as to the physiology of con- 
ception the inheritance of the psychic qualities of the 
two parents is of particular importance for psycho- 
logical purposes. It is well known that every child 
inherits from both his parents peculiarities of char- 
acter, temperament, talent, acuteness of sense, and 
strength of will. It is equally well known that even 
psychic qualities are often (if not always) transmitted 
from grandparents by heredity often, in fact, a man 
resembles his grandparents more than his parents in 


certain respects; and that is true both of bodily and 
mental features. All the chief laws of heredity which 
I first formulated in my General Morphology, and pop- 
ularized in my Natural History of Creation, are just as 
valid and universal in their application to psychic phe- 
nomena as to bodily structure in fact, they are fre- 
quently more striking and conspicuous in the former 
than in the latter. 

However, the great province of heredity, to the ines- 
timable importance of which Darwin first opened our 
eyes in 1859, is thickly beset with obscure problems and 
physiological difficulties. We dare not claim, even af- 
ter forty years of research, that all its aspects are clear 
to us. Yet we have done so much that we can confi- 
dently speak of heredity as a physiological function of 
the organism, which is directly connected with the fac- 
ulty of generation ; and we must reduce it, like all other 
vital phenomena, to exclusively physical and chemical 
processes, to the mechanics of the protoplasm. We now 
know accurately enough the process of impregnation 
itself ; we know that in it the nucleus of the spermato- 
zoon contributes the qualities of the male parent, and 
the nucleus of the ovum gives the qualities of the 
mother, to the newly born stem-cell. The blending of 
the two nuclei is the "physiological moment" of 
heredity ; by it the personal features of both body and 
soul are transmitted to the new individual. These 
facts of ontogeny are beyond the explanation of the 
dualistic and mystic psychology which still prevails 
in the schools ; whereas they find a perfectly simple in- 
terpretation in our monistic philosophy. 

The physiological fact which is most material for a 
correct appreciation of individual psychogeny is the con- 
tinuity of the psyche through the rise and fall of genera- 



tions. A new individual comes into existence at the 
moment of conception; yet it is not an independent 
entity, either in respect of its mental or its bodily feat- 
ures, but merely the product of the blending of the two 
parental factors, the maternal egg-cell and paternal 
sperm-cell. The cell-souls of these two sexual cells 
combine in the act of conception for the formation of a 
new cell-soul, just as truly as the two cell-nuclei, which 
are the material vehicles of this psychic potential en- 
ergy, unite to form a new nucleus. As we now see that 
the individuals of one and the same species even sis- 
ters born of the same parents always show certain 
differences, however slight, we must assume that these 
variations were already present in the chemical plas- 
matic constitution of the generative cells themselves.* 
These facts alone would suffice to explain the infinite 
variety of individual features, of soul and of bodily 
form, that we find in the organic world. As an ex- 
treme, but one-sided, consequence of them, there is the 
theory of Weismann, which considers the amphimixis, 
or the blending of the germ-plasm in sexual generation, 
to be the universal and the sole cause of individual vari- 
ability. This exclusive theory, which is connected with 
his theory of the continuity of the germ-plasm, is, in 
my opinion, an exaggeration. I am convinced, on the 
contrary, that the great laws of progressive heredity and 
of the correlative functional adaptation apply to the soul 
as well as to the body. The new characteristics which 
the individual has acquired during life may react to 
some extent on the molecular texture of the germ- 
plasm in the egg-cell and sperm-cell, and may thus 
be transferred to the next generation by heredity in 

* Law of individual variation. Vide Natural History of Cre- 



certain conditions (naturally, only in the form of latent 

Although in the soul-blending at the moment of con- 
ception only the latent forces of the two parent souls are 
transmitted by the coalescence of the erotic cell-nuclei, 
still it is possible that the hereditary psychic influence 
of earlier, and sometimes very much older, generations 
may be communicated at the same time. For the laws 
of latent heredity or atavism apply to the soul just as 
validly as to the anatomical organization. We find 
these remarkable phenomena of reversion in a very sim- 
ple and instructive form in the alternation of genera- 
tions of the polyps and medusae. Here we see two very 
different generations alternate so regularly that the 
first resembles the third, fifth, and so on ; while the sec- 
ond (very different from the preceding) is like the fourth, 
sixth, etc. (Natural History of Creation). We do not 
find such alternation of generations in man and the 
higher animals and plants, in which, owing to continu- 
ous heredity, each generation resembles the next ; nev- 
ertheless, even in these cases we often meet with phe- 
nomena of reversion, which must be reduced to the same 
law of latent heredity. 

Eminent men often take more after their grand- 
parents than their parents even in the finer shades of 
psychic activity in the possession of certain artistic 
talents or inclinations, in force of character, and in 
warmth of temperament; not infrequently there is a 
striking feature which neither parents nor grandpar- 
ents possessed, but which may be traced a long way back 
to an older branch of the family. Even in these re- 
markable cases of atavism the same laws of heredity 
apply to the psyche and to the physiognomy, to the per- 
sonal quality of the sense-organs, muscles, skeleton, 



and other parts of the body. We can trace them most 
clearly in the reigning dynasties and in old families 
of the nobility, whose conspicuous share in the life of 
the State has given occasion to a more careful historical 
picture of the individuals in the chain of generations 
for instance, in the Hohenzollerns, the princes of 
Orange, the Bourbons, etc., and in the Roman Caesars. 

The causal-nexus of biontic (individual) and phyletic 
(historical) evolution, which I gave in my General 
Morphology as the supreme law at the root of all bio- 
genetic research, has a universal application to psy- 
chology no less than to morphology. I have fully 
treated the special importance which it has with re- 
gard to man, in both respects, in the first chapter of 
my Anthropogeny. In man, as in all other organisms, 
" the embryonic development is an epitome of the his- 
torical development of the species. This condensed 
and abbreviated recapitulation is the more complete 
in proportion as the original epitomized development 
(palingenesis) is preserved by a constant heredity; 
on the other hand, it falls off from completeness in 
proportion as the later disturbing development (ceno- 
genesis) is accentuated by varying adaptation." 

While we apply this law to the evolution of the soul, 
we must lay special stress on the injunction to keep 
both sides of it critically before us. For, in the case of 
man, just as in all the higher animals and plants, such 
appreciable perturbations of type (or cenogeneses) have 
taken place during the millions of years of develop- 
ment that the original simple idea of palingenesis, or 
"epitome of history," has been greatly disturbed and 
altered. While, on the one side, the palingenetic re- 
capitulation is preserved by the laws of like-time and 
like-place heredity, it is subject to an essential ceno- 


genetic change, on the other hand, by the laws of abbre- 
viated and simplified heredity. That is clearly seen 
in the embryonic evolution of the psychic organs, the 
nervous system, the muscles, and the sense-organs. 
But it applies in just the same manner to the psychic 
functions, which are absolutely dependent on the nor- 
mal construction of these organs. Their evolution is 
subject to great cenogenetic modification in man and 
all other viviporous animals, precisely because the com- 
plete development of the embryo occupies a longer time 
within the body of the mother. But we have to distin- 
guish two periods of individual psychogeny: (i) the 
embryonic, and (2) the post-embryonic development of 
the soul. 

I. Embryonic Psychogeny. The human foetus, or 
embryo, normally takes nine months (or two hundred 
and seventy days) to develop in the uterus. During 
this time it is entirely cut off from the outer world, and 
protected, not only by the thick muscular wall of the 
womb, but also by the special foetal membranes (em- 
bryolemmata) which are common to all the three higher 
classes of vertebrates reptiles, birds, and mammals. 
In all the classes of amniotes these membranes (the 
amnion and the serolemma) develop in just the same 
fashion. They represent the protective arrangements 
which were acquired by the earliest reptiles (prorep- 
tilia), the common parents of all the amniotes, in the 
Permian period (towards the end of the palaeozoic age), 
when these higher vertebrates accustomed themselves 
to live on land and breathe the atmosphere. Their 
ancestors, the amphibia of the Carboniferous period, 
still lived and breathed in the water, like their earlier 
predecessors, the fishes. 

In the case of these older and lower vertebrates thai 


lived in the water, the embryonic development had the 
palingenetic character in a still higher degree, as is 
the case in most of the fishes and amphibia of the pres- 
ent day. The familiar tadpole and the larva of the 
salamander or the frog still preserve the structure of 
their fish-ancestors in the first part of their life in the 
water ; they resemble them, likewise, in their habits of 
life, in breathing by gills, in the action of their sense- 
organs, and in other psychic organs. Then, when the 
interesting metamorphosis of the swimming tadpole 
takes place, and when it adapts itself to a land-life, the 
fish-like body changes into that of a four-footed, crawl- 
ing amphibium; instead of the gill-breathing in the 
water comes an exclusive breathing of the atmosphere 
by means of lungs, and, with the changed habits of 
life, even the psychic apparatus, the nervous system, 
and the sense-organs reach a higher degree of con- 
struction. If we could completely follow the psychog- 
eny of the tadpole from beginning to end, we should be 
able to apply the biogenetic law in many ways to its 
psychic evolution. For it develops in direct commu- 
nication with the changing conditions of the outer 
world, and so must quickly adapt its sensation and 
movement to these. The swimming tadpole has not 
only the structure but the habits of life of a fish, and 
only acquires those of a frog in its metamorphosis. 

It is different with man and all the other amniotes ; 
their embryo is entirely withdrawn from the direct in- 
fluence of the outer world, and cut off from any recip- 
rocal action therewith, by enclosure in its protective 
membranes. Besides, the special care of the young 
on the part of the amniotes gives their embryo much 
more favorable conditions for the cenogenetic abbre- 
viation of the palingenetic evolution. There is, in the 


first place, the excellent arrangement for the nourish- 
ment of the embryo ; in the reptiles, birds, and mono- 
tremes (the oviparous mammals) it is effected by the 
great yellow nutritive yelk, which is associated with 
the egg ; in the rest of the mammals (the marsupials 
and placentals) it is effected by the mother's blood, 
which is conducted to the foetus by the blood-vessels 
of the yelk-sac and the allantois. In the case of the 
most highly developed placentals this elaborate nutri- 
tive arrangement has reached the highest degree of 
perfection by the construction of a placenta ; hence in 
these classes the embryo is fully developed before birth. 
But its soul remains during all this time in a state of 
embryonic slumber, a state of repose which Preyer has 
justly compared to the hibernation of animals. We 
have a similar long sleep in the chrysalis stage of those 
insects which undergo a complete metamorphosis- 
butterflies, bees, flies, beetles, and so forth. This sleep 
of the pupa, during which the most important forma- 
tions of organs and tissues take place, is the more in- 
teresting from the fact that the preceding condition of 
the free larva (caterpillar, grub, or maggot) included 
a highly developed psychic activity, and that this is, 
significantly, lower than the stage which is seen after- 
wards (when the chrysalis sleep is over) in the perfect, 
winged, sexually mature insect. 

Man's psychic activity, like that of most of the high- 
er animals, runs through a long series of stages of de- 
velopment during the individual life. We may single 
out the five following as the most important of them : 

I. The soul of the new-born infant up to the birth 
of self-consciousness and the learning of speech. 

II. The soul of the boy or girl up to puberty (i.e., 
until the awakening of the sexual instinct). 



III. The soul of the youth or maiden up to the time 
of sexual intercourse (the " idealist " period). 

IV. The soul of the grown man and the mature 
woman (the period of full maturity and of the found- 
ing of families, lasting until about the sixtieth year 
for the man and the fiftieth for the woman until in- 
volution sets in). 

V. The soul of the old man or woman (the period 
of degeneration). 

Man's psychic life runs the same evolution upward 
progress, full maturity, and downward degeneration 
as every other vital activity in his organization. 


Gradual Historical Evolution of the Human Soul from the Animal 
Soul Methods of Phylogenetic Psychology Four Chief 
Stages in the Phylogeny of the Soul : I. The Cell-Soul (Cyto- 
psyche) of the Protist (Infusoria, Ova, etc.) : Cellular Psychol- 
ogy ; II. The Soul of a Colony of Cells, or the Cenobitic Soul 
(Ccenopsyche) : Psychology of the Morula and Blastula ; III. 
The Soul of the Tissue (Histopsyche) : Its Twofold Nature : 
The Soul of the Plant: The Soul of the Lower, Nerveless 
Animal : Double Soul of the Siphonophora (Personal and Kor- 
mal Soul) ; IV. The Nerve-Soul (Neuropsyche) of the Higher 
Animal Three Sections of its Psychic Apparatus : Sense- 
Organs, Muscles, and Nerves Typical Formation of the 
Nerve-Centre in the Various Groups of Animals Psychic 
Organ of the Vertebrate : the Brain and the Spinal Cord 
Phylogeny of the Mammal Soul. 

r "THE theory of descent, combined with anthropolog- 
* ical research, has convinced us of the descent of 
our human organism from a long series of animal an- 
cestors by a slow and gradual transformation occupy- 
ing many millions of years. Since, then, we cannot 
dissever man's psychic life from the rest of his vital 
functions we are rather forced to a conviction of the 
natural evolution of our whole body and mind it be- 
comes one of the main tasks of the modern monistic 
psychology to trace the stages of the historical develop- 
ment of the soul of man from the soul of the brute. Our 
* phylogeny of the soui " seeks to attain this object; it 



may also, as a branch of general psychology, be called 
phylogenetic psychology, or, in contradistinction to bi- 
ontic (individual), phyletic psychogeny. And, although 
this new science has scarcely been taken up in earnest 
yet, and most of the " professional " psychologists deny 
its very right to existence, we must claim for it the ut- 
most importance and the deepest interest. For, in our 
opinion, it is its special province to solve for us the 
great enigma of the nature and origin of the human 

The methods and paths which will lead us to the re- 
mote goal of a complete phylogenetic psychology a 
goal that is still buried in the mists of the future, and 
almost imperceptible to many do not differ from those 
of other branches of evolutionary research. Compar- 
ative anatomy, physiology, and ontogeny are of the first 
importance. Much support is given also by palaeon- 
tology, for the order in which the fossil remains of the 
various classes of vertebrates succeed each other in the 
course of organic evolution reveals to us, to some ex- 
tent, the gradual growth of their psychic power as well 
as their phyletic connection. We must admit that we 
are here, as we are in every branch of phylogenetic re- 
search, driven to the construction of a number of hy- 
potheses in order to fill up the considerable lacunae of 
empirical phylogeny. Yet these hypotheses cast so 
clear and significant a light on the chief stages of his- 
torical development that we are afforded a most gratify- 
ing insight into their entire course. 

The comparative psychology of man and the higher 
animals enables us to learn from the highest group of 
the placentals, the primates, the long strides by which 
the human soul has advanced beyond the psyche of the 
anthropoid ape. The phylogeny of the mammals and of 



the lower vertebrates acquaints us with the long series 
of the earlier ancestors of the primates which have arisen 
within this stem since the Silurian age. All these ver- 
tebrates agree in the structure and development of their 
characteristic psychic organ the spinal cord. We 
learn from the comparative anatomy of the vermalia 
that this spinal cord has been evolved from a dorsal aero- 
ganglion, or vertical brain, of an invertebrate ancestor. 
We learn, further, from comparative ontogeny that this 
simple psychic organ has been evolved from the stratum 
of cells in the outer germinal layer> the ectoderm, of the 
platodes. In these earliest flat-worms, which have no 
specialized nervous system, the outer skin -covering 
serves as a general sensitive and psychic organ. Fi- 
nally, comparative embryology teaches us that these 
simple metazoa have arisen by gastrulation from blas- 
taeades, from hollow spheres, the wall of which is merely 
one simple layer of cells, the blastoderm ; and the same 
science, with the aid of the biogenetic law, explains how 
these protozoic coenobia originally sprang from the sim- 
plest unicellular organisms. 

On a critical study of these different embryonic for- 
mations, the evolution of which from each other we can 
directly observe under the microscope, we arrive, by 
means of the great law of biogeny, at a series of most 
important conclusions as to the chief stages in the de- 
velopment of our psychic life. We may distinguish 
eight of these to begin with : 

I. Unicellular protozoa with a simple cell-soul : the 

II. Multicellular protozoa with a communal soul: 
the catallacta. 

III. The earliest metazoa with an epithelial soul: 
the platodes. 


IV. Invertebrate ancestors with a simple vertical 
brain : the vermalia. 

V. Vertebrates without skull or brain, with a simple 
spinal cord: the acrania. 

VI. Animals with skull and brain (of five vesicles) : 
the craniota. 

VII. Mammals with predominant development of the 
cortex of the brain : the placentals. 

VIII. The higher anthropoid apes and man, with 
organs of thought (in the cerebrum) : the anthropo- 

Among these eight stages in the development of the 
human soul we may further distinguish more or less 
clearly a number of subordinate stages. Naturally, 
however, in reconstructing them we have to fall back 
on the same defective evidence of empirical psychology 
which the comparative anatomy and physiology of the 
actual fauna affords us. As the craniote animals of 
the sixth stage and these are true fishes are already 
found fossilized in the Silurian system, we are forced to 
assume that the five preceding series of ancestors (which 
were incapable of fossilization) were evolved in an ear- 
lier, pre-Silurian age. 

I. The cell-soul (or cytopsyche) : first stage of phyletic 
psychogenesis. The earliest ancestors of man and all 
other animals were unicellular protozoa. This fun- 
damental hypothesis of rational phylogeny is based, 
in virtue of the phylogenetic law, on the familiar em- 
bryological fact that every man, like every other 
metazoon (i.e., every multicellular organism with tis- 
sues), begins his personal existence as a simple cell, 
the stem -cell (cytula), or the impregnated egg -cell 
(see p. 63). As this cell has a "soul" from the com- 
mencement, so had also the corresponding unicellu- 


lar ancestral forms, which were represented in the old- 
est series of man's ancestors by a number of different 

We learn the character of the psychic activity of 
these unicellular organisms from the comparative 
physiology of the protists of to-day. Close observa- 
tion and careful experiment have opened out to us in 
this respect, in the second half of the nineteenth cen- 
tury, a new world of the most interesting phenomena. 
The best description of them was given by Max Ver- 
worn in his thoughtful work, based on original re- 
search, Psycho-physiological Studies of the Protists. 
The work includes also the few earlier observations 
of the "psychic life of the protist." Verworn came to 
the firm conclusion that the psychic processes are un- 
conscious in all the protists, that the phenomena of 
sensation and movement coincide with the molecular 
vital processes in their protoplasm, and that their ulti- 
mate causes are to be sought in the properties of the 
protoplasmic molecules (the plastidules) . " Hence the 
psychic phenomena of the protists form a bridge that 
connects the chemical processes of the inorganic world 
with the psychic life of the highest animals; they 
represent the germ of the highest psychic phenomena 
of the metazoa and of man." 

The careful observations and many experiments of 
Verworn, together with those of Wilhelm Engelmann, 
Wilhelm Preyer, Richard Hertwig, and other more 
recent students of the protists, afford conlcusive evi- 
dence for my "theory of the cell-soul" (1866). On the 
strength of several years of study of different kinds 
of protists, especially rhizopods and infusoria, I pub- 
lished a theory thirty-three years ago to the effect that 
every living cell has psychic properties, and that the 



psychic life of the multicellular animals and plants is 
merely the sum total of the psychic functions of the 
cells which build up their structure. In the lower 
groups (in algae and sponges, for instance) all the cells 
of the body have an equal share in it (or with very slight 
differences) ; in the higher groups, in harmony with 
the law of the " division of labor/' only a select portion 
of them are involved the "soul-cells." The impor- 
tant consequences of this a cellular psychology " were 
partly treated in my work on The Perigenesis of the 
Plastidule (1876), and partly in my speech at Munich, 
in 1877, on " Modern Evolution in Relation to the Whole 
of Science." A more popular presentation of them 
is to be found in my two Vienna papers (1878) on " The 
Origin and Development of the Sense-Organs" and 
on "Cell-Souls and Soul-Cells." 

Moreover, the cell-soul, even within the limits of the 
protist world, presents a long series of stages of devel- 
opment, from the most simple and primitive to a com- 
paratively elaborate activity. In the earliest and sim- 
plest protists the faculty of sensation and movement 
is equally distributed over the entire protoplasm of the 
homogeneous morsel ; in the higher forms certain " cell- 
instruments," or organdla, appear, as their physio- 
logical organs. Motor cell-parts of that character are 
found in the pseudopodia of the rhizopods, and the vi- 
brating hairs, lashes, or cilia of the infusoria. The 
cell-nucleus, which is wanting in the earlier and lower 
protists, is considered to be an internal central organ 
of the cell-life. It is especially noteworthy, from a 
physiologico-chemical point of view, that the very ear- 
liest protists were plasmodomous, with plant-like nu- 
trition hence protophyta, or primitive plants; from 
these came as a secondary stage, by metasitism, the 


first plasmophagi, with animal nutrition the proto- 
zoa, or primitive animals.* This metasitism, or cir- 
culation of nutritive matter, implies an important psy- 
chological advance; with it began the development 
of those characteristic properties of the animal soul 
which are wanting in the plant. 

We find the highest development of the animal cell- 
soul in the class of ciliata, or ciliated infusoria. When 
We compare their activity with the corresponding psy- 
chic life of the higher, multicellular animals, we find 
scarcely any psychological difference; the sensitive 
and motor organella of these protozoa seem to accom- 
plish the same as the sense-organs, nerves, and muscles 
of the metazoa. Indeed, we have found in the great 
cell-nucleus (meganucleus) of the infusoria a central 
organ of psychic activity, which plays much the same 
part in their unicellular organism as the brain does 
in the psychic life of higher animals. However, it is 
very difficult to determine how far this comparison is 
justified; the views of experts diverge considerably 
over the matter. Some take all spontaneous bodily 
movement in them to be automatic, or impulsive, and 
all stimulated movement to be reflex; others are con- 
vinced that such movements are partly voluntary and 
intentional. The latter would attribute to the infusoria 
a certain degree of consciousness, and even self-con- 
sciousness; but this is rejected by the others. How- 
ever that very difficult question may be settled, it does 
not alter the fact that these unicellular protozoa give 
proof of the possession of a highly developed "cell- 
soul," which is of great interest for a correct decision 
as to the psyche of our earliest unicellular ancestors. 

* Cf. E. Haeckel, Systematic Phytogeny, vol. i. 


II. The communal or cenobitic soul (coenopsyche) : 
second stage of phyletic psychogenesis. Individual 
development begins, in man and in all other multi- 
cellular animals, with the repeated segmentation of 
one simple cell. This stem-cell, the impregnated ovum, 
divides first into two daughter cells, by a process of 
ordinary indirect segmentation; as the process is re- 
peated there arise (by equal division of the egg) suc- 
cessively four, eight, sixteen, thirty-two, sixty -four 
such new cells, or " blastomeres." Usually (that is, 
in the case of the majority of animals) an irregular en- 
largement sooner or later takes the place of this original 
regular division of cells. But the result is the same 
in all cases the formation of a (generally spherical) 
cluster of heterogeneous (originally homogeneous) 
cells. This stage is called the morula ("mulberry," 
which it somewhat resembles in shape). Then, as 
a rule, a fluid gathers in the interior of this aggregate of 
cells; it changes into a spherical vesicle; all the cells 
go to its surface, and arrange themselves in one simple 
layer the blastoderm. The hollow sphere which is 
thus formed is the important stage of the "germinal 
vesicle," the blastula, or blastosphere. 

The psychological phenomena which we directly 
observe in the formation of the blastula are partly 
sensations, partly movements, of this community of 
cells. The movements may be divided into two groups : 

(1) the inner movements, which are always repeated in 
substantially the same manner in the process of or- 
dinary (indirect) segmentation of cells (formation of 
the axis of the nucleus, mitosis, karyokinesis, etc.) ; 

(2) the outer movements, which are seen in the 
regular change of position of the social cells and 
their grouping for the construction of the blastoderm. 


We assume that these movements are hereditary and 
unconscious, because they are always determined in 
the same fashion by heredity from the earlier protist 
ancestors. The sensations also fall into two groups : 
(i) the sensations of the individual cells, which reveal 
themselves in the assertion of their individual inde- 
pendence and their relation to neighboring cells (with 
which they are in contact, and partly in direct com- 
bination, by means of protoplasmic fibres) ; (2) the 
common sensation of the entire community of cells, 
which is seen in the individual formation of the blastula 
as a hollow vesicle. 

The causal interpretation of the formation of the 
blastula is given us by the biogenetic law, which ex- 
plains the phenomena we directly observe to be the 
outcome of heredity, and relates them to correspond- 
ing historical processes which took place long ago in 
the origin of the earliest protist-coenobia, the blastseads. 
But we get a physiological and psychological insight 
into these important phenomena of the earliest cell- 
communities by observation and experiment on their 
modern representatives. Such permanent cell -com- 
munities or colonies are still found in great numbers 
both among the plasmodomous primitive plants (for 
instance, the paulotomacea, diatomacea, volvocinae, 
etc.) and the plasmophagous primitive animals (the 
infusoria and rhizopods). In all these coenobia we 
can easily distinguish two different grades of psychic 
activity: (i) the cell-soul of the individual cells (the 
" elementary organisms ") and (2) the communal soul 
of the entire colony. 

III. The tissue -soul (histopsyche) : third stage of 
phyletic psychogenesis. In all multicellular, tissue- 
forming plants (metaphyta) and in the lowest, nerve- 


less classes of tissue-forming animals (metazoa) we 
have to distinguish two different forms of psychic ac- 
tivity namely : (i) the psyche of the individual cells 
which compose the tissue, and (2) the psyche of the tis- 
sue itself, or of the " cell-state " which is made up of the 
tissues. This " tissue-soul " is the higher psychologi- 
cal function which gives physiological individuality to 
the compound multicellular organism as a true "cell- 
commonwealth." It controls all the separate " cell- 
souls " of the social cells the mutually dependent 
"citizens" which constitute the community. This fun- 
damental twofold character of the psyche in the meta- 
phyta and the lower, nerveless metazoa is very impor- 
tant. It may be verified by unprejudiced observation 
and suitable experiment. In the first place, each sin- 
gle cell has its own sensation and movement, and, in 
addition, each tissue and each organ, composed of a 
number of homogeneous cells, has its special irritabil- 
ity and psychic unity (e.g., the pollen and stamens). 

A. The plant-soul (phytopsyche) is, in our view, the 
summary of the entire psychic activity of the tissue- 
forming, multicellular plant (the metaphyton, as dis- 
tinct from the unicellular protophyton) ; it is, however, 
the subject of the most diverse opinions even at the 
present day. It was once customary to draw an essen- 
tial distinction between the plant and the animal, on 
the ground that the latter had a " soul " and the plant 
had none. However, an unprejudiced comparison of 
the irritability and movements of various higher plants 
and lower animals convinced many observers, even at 
the beginning of the century, that there must be a 
" soul " on both sides. At a later date Fechner, Leit- 
geb, and others strongly contended for the plant-soul. 
But a profounder knowledge of the subject was ob- 


tained when the similarity of the elementary structure 
of the plant and of the animal was proved by the cellu- 
lar theory, and especially when the similarity of con- 
duct of the active, living protoplasm in both was shown 
in the plasma theory of Max Schultze (1859). Modern 
comparative physiology has shown that the physio- 
logical attitude towards various stimuli (light, heat, 
electricity, gravity, friction, chemical action, etc.) of 
the " sensitive " portions of many plants and animals 
is exactly the same, and that the reflex movements 
which the stimuli elicit take place in precisely the same 
manner on both sides. Hence, if it was necessary to 
attribute this activity to a " soul " in the lower, nerveless 
metazoa (sponges, polyps, etc.), it was also necessary 
in the case of many (if not all) metaphyta, at least in the 
very sensitive mimosa, the " fly-traps " (dionaea and 
drosera), and the numerous kinds of climbing plants. 
It is true that modern vegetal physiology has given 
a purely physical explanation of many of these stimu- 
lated movements, or tropisms, by special features of 
growth, variations of pressure, etc. Yet these me- 
chanical causes are neither more nor less psychophysi- 
cal than the similar " reflex movements " of the sponges, 
polyps, and other nerveless metazoa, even though 
their mechanism is entirely different. The character of 
the tissue-soul reveals itself in the same way in both 
cases the cells of the tissue (the regular, orderly struct- 
ure of cells) transmit the stimuli they have received 
in one part, and thus provoke movements of other 
parts, or of the whole organ. This transmission of 
stimuli has as much title to be called " psychic activity " 
as its more complete form in the higher animals with 
nerves ; the anatomic explanation of it is that the social 
cells of the tissue, or cell-community, are not isolated 



from each other (as was formerly supposed), but are 
connected throughout by fine threads or bridges of 
protoplasm. When the sensitive mimosa closes its 
graceful leaves and droops its stalk at contact, or on 
being shaken ; when the irritable fly-trap (the diona3a) 
swiftly clasps its leaves together at a touch, and capt- 
ures a fly ; the sensation seems to be keener, the trans- 
mission of the stimulus more rapid, and the movement 
more energetic than in the reflex action of the stimu- 
lated bath-sponge and many other sponges. 

B. The soul of the nerveless metazoa. Of very special 
interest for comparative psychology in general, and for 
the phylogeny of the animal soul in particular, is the 
psychic activity of those lower metazoa which have 
tissues, and sometimes differentiated organs, but no 
nerves or specific organs of sense. To this category 
belong four different groups of the earliest coelen- 
terates: (a) the gastrseads, (6) the platodaria, (c) the 
sponges, and (d) the hydropolyps, the lowest form of 

The gastraeads (or animals with a primitive gut) 
form a small group of the lowest coelenterates, which 
is of great importance as the common ancestral group 
of all the metazoa. The body of these little swimming 
animals looks like a tiny (generally oval) vesicle, 
which has a simple cavity with one opening the prim- 
itive gut and the primitive mouth. The wall of the di- 
gestive cavity is formed of two simple layers of cells, 
or epithelium, the inner of which the gut-layer is 
responsible for the vegetal activity of nourishment, 
while the outer, or skin-layer, discharges the animal 
functions of movement and sensation. The homoge- 
neous sensitive cells of the skin-layer bear long, slender 
hairs or lashes (cilia), by the vibration of which the 


swimming motion is effected. The few surviving forms 
of gastraeads, the gastraemaria (trichoplacidae) and cye- 
maria (orthonectidae) , are extremely interesting, from 
the fact that they remain throughout life at a stage 
of structure which is passed by all the other metazoa 
(from the sponge to man) at the commencement of their 
embryonic development. As I have shown in my The- 
ory of the Gastraea (1872), a very characteristic embry- 
onic form, the gastrula, is immediately developed from 
the blastula in all the tissue animals. The germinal 
membrane (blastoderm), which represents the wall of 
the hollow vesicle, forms a depression at one side, and 
this soon sinks in so deep that the inner cavity of the 
vesicle disappears. The half of the membrane which 
bends in is thus laid on, and inside, the other half; 
the latter forms the skin-layer, or outer germinal layer 
(ectoderm or epiblast), and the former becomes the gut- 
layer, or inner germinal layer (endoderm or hypoblast). 
The new cavity of the cup-shaped body is the digestive 
stomach cavity (the progaste), and its opening is the 
primitive mouth (or prostoma)* The skin-layer, or ec- 
toderm, is the primitive psychic organ in the metazoa ; 
from it, in all the nerve animals, not only the external 
skin and the organs of sense, but also the nervous sys- 
tem, are developed. In the gastraeads, which have no 
nerves, all the cells which compose the simple epithe- 
lium of the ectoderm are equally organs of sensation 
and of movement ; we have here the tissue-soul in its 
simplest form. 

The platodaria, the earliest and simplest form of the 
platodes, seem to be of the same primitive construction. 
Some of these cryptocoela the convoluta, etc. have 

* Cf . Anthropogeny and Natural History of Creation. 


no specific nervous system, while their nearest rela- 
tives, the turbellaria, have already differentiated one, 
and even developed a vertical brain. 

The sponges form a peculiar group in the animal world, 
which differs widely in organization from all the other 
metazoa. The innumerable kinds of sponges grow, as 
a rule, at the bottom of the sea. The simplest form of 
sponge, the olynthus, is in reality nothing more than a 
gastraea, the body-wall of which is perforated like a 
sieve, with fine pores, in order to permit the entrance of 
the nourishing stream of water. In the majority of 
sponges even in the most familiar one, the bath-sponge 
the bulbous organism constructs a kind of stem or tree, 
which is made up of thousands of these gastraeads, and 
permeated by a nutritive system of canals. Sensation 
and movement are only developed in the faintest degree 
in the sponges ; they have no nerves, muscles, or organs 
of sense. It was therefore quite natural that such 
stationary, shapeless, insensitive animals should have 
been commonly taken to be plants in earlier years. 
Their psychic life for which no special organs have 
been differentiated is far inferior to that of the mi- 
mosa and other sensitive plants. 

The soul of the cnidaria is of the utmost importance 
in comparative and phylogenetic psychology ; for in this 
numerous group of the ccelenterates the historical evo- 
lution of the nerve-soul out of the tissue-soul is repeated 
before our eyes. To this group belong the innumerable 
classes of stationary polyps and corals, and of swim- 
ming medusa3 and siphonophora. As the common an- 
cestor of all the cnidaria we can safely assign a very sim- 
ple polyp, which is substantially the same in structure 
as the common, still surviving, fresh-water polyp the 
hydra. Yet the hydrse, and the stationary, closely re- 



lated hydropolyps, have no nerves or higher sense-or- 
gans, although they are extremely sensitive. On the 
other hand, the free-swimming medusae, which are de- 
veloped from them and are still connected with them by 
alternation of generations have an independent ner- 
vous system and specific sense-organs. Here, also, we 
may directly observe the ontogenetic evolution of the 
nerve-soul (neuropsyche) out of the tissue-soul (histo- 
psyche), and thus learn its phylogenetic origin. This 
is the more interesting as such phenomena are polyphy- 
letic that is, they have occurred several times more 
than once, at least quite independently. As I have 
shown elsewhere, the hydromedusae have arisen from the 
hydropolyps in a different manner from that of the evo- 
lution of the scyphomedusae from the scyphopolyps ; 
the gemmation is terminal in the case of the latter, and 
lateral with the former. In addition, both groups have 
characteristic hereditary differences in the more minute 
structure of their psychic organs. The class of siphon- 
ophora is also very interesting to the psychologist. In 
these pretty, free-swimming organisms, which come 
from the hydromedusae we can observe a double soul : 
the personal soul of the numerous individualities which 
compose them, and the common, harmoniously acting 
psyche of the entire colony. 

IV. The rferve-soul (neuropsyche) : fourth stage of 
phyletic psychogeny. The psychic life of all the higher 
animals is conducted, as in man, by means of a more or 
less complicated "psychic apparatus." This appara- 
tus is always composed of three chief sections : the or- 
gans of sense are responsible for the various sensations ; 
the muscles effect the movements ; the nerves form the 
connection between the two by means of a special cen- 
tral organ, the brain or ganglion. The arrangement 



and action of this psychic mechanism have been fre- 
quently compared with those of a telegraphic system : 
the nerves are the wires, the brain the central, and the 
sense-organs subordinate stations. The motor nerves 
conduct the commands of the will centrif ugally from the 
nerve-centre to the muscles, by the contraction of which 
they produce the movements : the sensitive nerves trans- 
mit the various sensations centripetally that is, from 
the peripheral sense-organs to the brain, and thus ren- 
der an account of the impressions they receive from the 
outer world. The ganglionic cells, or "psychic cells," 
which compose the central nervous organ, are the most 
perfect of all organic elements ; they not only conduct 
the commerce between the muscles and the organs of 
sense, but they also effect the highest performances of 
the animal soul, the formation of ideas and thoughts, 
and especially consciousness. 

The great progress of anatomy, physiology, his- 
tology, and ontogeny has recently added a wealth 
of interesting discoveries to our knowledge of the 
mechanism of the soul. If speculative philosophy 
assimilated only the most important of these signif- 
icant results of empirical biology, it would have a very 
different character from that it unfortunately presents. 
As I have not space for an exhaustive treatment of 
them here, I will confine myself to a relation of the chief 

Each of the higher animal species has a character- 
istic psychic organ; the central nervous system of 
each has certain peculiarities of shape, position, and 
composition. The medusae, among the radiating 
cnidaria, have a ring of nervous matter at the border 
of the fringe, generally provided with four or eight 
ganglia. The mouth of the five-rayed cnidarion is 



girt with a nerve-ring, from which proceed five branches. 
The bi-symmetrical platodes and the vermalia have a 
vertical brain, or acroganglion, composed of two dorsal 
ganglia, lying above the mouth; from these "upper 
ganglia" two branch nerves proceed to the skin and 
the muscles. In some of the vermalia and in the mol- 
lusca a pair of ventral "lower ganglia" are added, 
which are connected with the former by a ring round 
the gullet. This ring is found also in the articulata; 
but in these it is continued on the belly side of the 
long body as a ventral medulla, a double fibre like a 
rope-ladder, which expands into a double ganglion in 
each member. The vertebrates have an entirely dif- 
ferent formation of the psychic organ; they have al- 
ways a spinal medulla developed at the back of the 
body; and from an expansion of its fore part there 
arises subsequently the characteristic vesicular brain.* 

Although the psychic organs of the higher species 
of animals differ very materially in position, form, and 
composition, nevertheless comparative anatomy is in 
a position to prove a common origin for most of them 
namely, from the vertical brain of the platodes and 
vermalia; they have all, moreover, had their origin 
in the outermost layer of the embryo, the ectoderm, or 
outer skin -layer. Hence we find the same typical 
structure in all varieties of the central nervous organ 
a combination of ganglionic cells, or "psychic cells" 
(the real active elementary organs of the soul), and of 
nerve -fibres, which effect the connection and trans- 
mission of the action. 

The first fact we meet in the comparative psychol- 
ogy of the vertebrates, and which should be the em* 

* Cf . Natural History of Creation. 


pirical starting-point of all scientific human psychology, 
is the characteristic structure of the central nervous 
system. This central psychic organ has a particular 
position, shape, and texture in the vertebrate as it has 
in all the higher species. In every case we find a spi- 
nal medulla, a strong cylindrical nervous cord, which 
runs down the middle of the back, in the upper part of 
the vertebral column (or the cord which represents it). 
In every case a number of nerves branch off from this 
medulla in regular division, one pair to each segment 
or vertebra. In every case this medullary cord arises 
in the same way in the foetus ; a fine groove appears 
in the middle axis of the skin at the back ; then the par- 
allel borders of this medullary groove are lifted up a 
little, bend over towards each other, and form into a 
kind of tube. 

The long dorsal cylindrical medullary tube which 
is thus formed is thoroughly characteristic of the ver- 
tebrates ; it is always the same in the early embryonic 
sketch of the organism, and it is always the chief feat- 
ure of the different kinds of psychic organ which evolve 
from it in time. Only one single group of invertebrates 
has a similar structure : the rare, marine tunicata, 
copelata, ascidia, and thalidiae. These animals have 
other important peculiarities of structure (especially 
in the chorda and the gut) which show a striking di- 
vergence from the other invertebrates and resemblance 
to the vertebrates. The inference we draw is that both 
these groups, the vertebrates and the tunicates, have 
arisen from a common ancestral group of the vermalia, 
the prochordonia* Still, there is a great difference 
between the two classes in the fact that the body of the 

* See chaps, xvi. and xvii. of my Anthropogeny. 



tunicate does not articulate, or form members, and has 
a very simple organization (most of them subsequently 
attach themselves to the bottom of the sea and degen- 
erate). The vertebrate, on the other hand, is charac- 
terized by an early development of internal members, 
and the formation of pro-vertebrae (vertebratio) . - This 
prepares the way for the much higher development of 
their organism, which finally attains perfection in man. 
This is easily seen in the finer structure of his spinal 
cord, and in the development of a number of segmental 
pairs of nerves, the spinal nerves, which proceed to the 
various parts of the body. 

The long ancestral history of our " vertebrate soul " 
commences with the formation of the most rudimentary 
spinal cord in the earliest acrania ; slowly and gradu- 
ally, through a period of many millions of years, it 
conducts to that marvellous structure of the human 
brain which seems to entitle the highest primate form 
to quite an exceptional position in nature. Since a 
clear conception of this slow and steady progress of 
our phyletic psychogeny is indispensable for a true 
psychology, we must divide that vast period into a 
number of stages or sections : in each of them the per- 
fecting of the structure of the nervous centre has been 
accompanied by a corresponding evolution of its func- 
tion, the psyche. I distinguish eight of these periods 
in the phylogeny of the spinal cord, which are charac- 
terized by eight different groups of vertebrates : (i) the 
acrania ; (2) the cyclostomata ; (3) the fishes ; (4) the 
amphibia ; (5) the implacental mammals (monotremes 
and marsupials) ; (6) the earlier placental mammals, 
especially the prosimiae; (7) the younger primates, 
the simiae ; and (8) the anthropoid apes and man. 

I. First stage the acrania: their only modern 



representative is the lancelot or amphioxus; the psy- 
chic organ remains a simple medullary tube, and con- 
tains a regularly segmented spinal cord, without brain. 

II. Second stage the cyclostomata : the oldest group 
of the craniota, now only represented by the petromy- 
zontes and myxinoides : the fore-termination of the 
cord expands into a vesicle, which then subdivides 
into five successive parts the great-brain, intermedi- 
ate-brain, middle-brain, little-brain, and hind-brain: 
these five cerebral vesicles form the common type from 
which the brain of all craniota has evolved, from the 
lamprey to man. 

III. Third stage the primitive fishes (selachii) : sim- 
ilar to the modern shark: in these oldest fishes, from 
which all the gnathostomata descend, the more pro- 
nounced division of the five cerebral vesicles sets in. 

IV. Fourth stage the amphibia. These earliest 
land animals, making their first appearance in the Car- 
boniferous period, represent the commencement of the 
characteristic structure of the tetrapod and a correspond- 
ing development of the fish-brain: it advances still 
further in their Permian successors, the reptiles, the 
earliest representatives of which, the tocosauria, are the 
common ancestors of all the amniota (reptiles and birds 
on one side, mammals on the other). 

V.-VIII. Fifth to the eighth stages the mammals. 
I have exhaustively treated, and illustrated with a num- 
ber of plates, in my Anthropogeny, the evolution of our 
nervous system and the correlative question of the de- 
velopment of the soul. I have now, therefore, merely 
to refer the reader to that work. It only remains for 
me to add a few remarks on the last and most interest- 
ing class of facts pertaining to this to the evolution of 
the soul and its organs within the limits of the class 



mammalia. In doing so, I must remind the reader 
that the monophyletic origin of this class that is, the 
descent of all the mammals from one common ancestral 
form (of the Triassic period) is now fully established. 
The most important consequence of the monophy- 
letic origin of the mammals is the necessity of deriving 
the human soul from a long evolutionary series of other 
mammal souls. A deep anatomical and physiological 
gulf separated the brain structure and the dependent 
psychic activity of the higher mammals from those of 
the lower: this gulf, however, is completely bridged 
over by a long series of intermediate stages. The pe- 
riod of at least fourteen (more than a hundred, on other 
estimates) million years, which has elapsed since the 
commencement of the Triassic period, is amply suffi- 
cient to allow even the greatest psychological advance. 
The following is a summary of the results of investi- 
gation in this quarter, which has recently been very 
penetrating : 

I. The brain of the mammal is differentiated from 
that of the other vertebrates by certain features, which 
are found in all branches of the class ; especially by a 
preponderant development of the first and fourth ves- 
icles, the cerebrum and cerebellum, while the third ves- 
icle, the middle brain, disappears altogether. 

II. The brain development of the lowest and earliest 
mammals (the monotremes, marsupials, and procho- 
riates) is closely allied to that of their palaeozoic ances- 
tors, the Carboniferous amphibia (the stegocephala) and 
the Permian reptiles (the tocosauria). 

III. During the Tertiary period commences the typ- 
ical development of the cerebrum, which distinguishes 
the younger mammals so strikingly from the older. 

IV. The special development (quantitatively and 

1 68 


qualitatively) of the cerebrum which is so prominent 
a feature in man, and which is the root of his pre- 
eminent psychic achievements, is only found, outside 
humanity, in a small section of the most highly devel- 
oped mammals of the earlier Tertiary epoch, especially 
in the anthropoid apes. 

V. The differences of brain structure and psychic 
faculty which separate man from the anthropoid ape 
are slighter than the corresponding interval between 
the anthropoid apes and the lower primates (the ear- 
liest simiae and prosimiae). 

VI. Consequently, the historical, gradual evolution 
of the human soul from a long chain of higher and 
lower mammal souls must, by application of the uni- 
versally valid phyletic laws of the theory of descent, 
be regarded as a fact which has been scientifically 


Consciousness as a Natural Phenomenon Its Definition Diffi- 
culties of the Problem Its Relation to the Life of the Soul 
Our Human Consciousness Various Theories : I. Anthro- 
pistic Theory (Descartes) ; II. Neurological Theory (Darwin) ; 
III. Animal Theory (Schopenhauer) ; IV. Biological Theory 
(Fechner) ; V. Cellular Theory (Fritz Schultze) ; VI. Atomistic 
Theory Monistic and Dualistic Theories Transcendental 
Character of Consciousness The Ignorabimus Verdict of 
Du Bois-Reymond Physiology of Consciousness Discov- 
ery of the Organs of Thought by Flechsig Pathology 
Double and Intermittent Consciousness Ontogeny of Con- 
sciousness : Modifications at Different Ages Phylogeny of 
Consciousness Formation of Concepts 

1MO phenomenon of the life of the soul is so wonder- 
" ^ 1 ul and so variously interpreted as consciousness. 
The most contradictory views are current to-day, as they 
were two thousand years ago, not only with regard to 
the nature of this psychic function and its relation to 
the body, but even as to its diffusion in the organic 
world and its origin and development. It is more re- 
sponsible than any other psychic faculty for the erro- 
neous idea of an " immaterial soul " and the belief in 
" personal immortality " ; many of the gravest errors 
that still dominate even our modern civilization may 
be traced to it. Hence it is that I have entitled con- 
sciousness "the central mystery of psychology"; it 



is the strong citadel of all mystic and dualistic er- 
rors, before whose ramparts the best-equipped efforts 
of reason threaten to miscarry. This fact would suf- 
fice of itself to induce us to make a special critical 
study of consciousness from our monistic point of view. 
We shall see that consciousness is simply a natural 
phenomenon like any other psychic quality, and that 
it is subject to the law of substance like all other nat-i 
ural phenomena. 

Even as to the elementary idea of consciousness, its 
contents and extension, the views of the most distin- 
guished philosophers and scientists are widely diver- 
gent. Perhaps the meaning of consciousness is best 
conceived as an internal perception, and compared with 
the action of a mirror. As its two chief departments 
we distinguish objective and subjective consciousness 
consciousness of the world, the non-ego, and of the 
ego. By far the greater part of our conscious activity, 
as Schopenhauer justly remarked, belongs to the con- 
sciousness of the outer world, or the non-ego: this 
world-consciousness embraces all possible phenomena 
of the outer world which are in any sense accessible to 
our minds. Much more contracted is the sphere of 
self-consciousness, the internal mirror of all our own 
psychic activity, all our presentations, sensations, and 

Many distinguished thinkers, especially on the phys- 
iological side (Wundt and Ziehen, for instance) take 
the ideas of consciousness and psychic function to be 
identical " all psychic action is conscious " ; the prov- 
ince of psychic life, they say, is coextensive with that 
of consciousness. In our opinion, such a definition 
gives an undue extension to the meaning of con- 
sciousness, and occasions many errors and misunder- 



standings. We share, rather, the view of other phi- 
losophers (Romanes, Fritz Schultze, and Paulsen), 
that even our unconscious presentations, sensations, 
and volitions pertain to 'our psychic life; indeed, 
the province of these unconscious psychic actions 
(reflex action, and so forth) is far more extensive 
than that of consciousness. Moreover, the two prov- 
inces are intimately connected, and are separated by 
no sharp line of demarcation. An unconscious pres- 
entation may become conscious at any moment; let 
our attention be withdrawn from it by some other ob- 
ject, and forthwith it disappears from consciousness 
once more. 

The only source of our knowledge of consciousness 
is that faculty itself; that is the chief cause of the 
extraordinary difficulty of subjecting it to scientific 
research. Subject and object are one and the same 
in it: the perceptive subject mirrors itself in its own 
inner nature, which is to be the object of our inquiry. 
Thus we can never have a complete objective certainty 
of the consciousness of others; we can only proceed 
by a comparison of their psychic condition with our 
own. As long as this comparison is restricted to nor- 
mal people we are justified in drawing certain conclu- 
sions as to their consciousness, the validity of which is 
unchallenged. But when we pass on to consider ab- 
normal individuals (the genius, the eccentric, the stu- 
pid, or the insane) our conclusions from analogy are 
either unsafe or entirely erroneous. The same must 
be said with even greater truth when we attempt to 
compare human consciousness with that of the animals 
(even the higher, but especially the lower). In that 
case such grave difficulties arise that the views of phys- 
iologists and philosophers diverge as widely as the 



poles on the subject. We shall briefly enumerate the 
most important of these views. 

I. The anthropistic theory of consciousness. It is pe- 
culiar to man. To Descartes we must trace the wide- 
spread notion that consciousness and thought are man's 
exclusive prerogative, and that he alone is blessed with 
an " immortal soul/' This famous French philosopher 
and mathematician (educated in a Jesuit College) es-i 
tablished a rigid partition between the psychic activity 
of man and that of the brute. In his opinion the hu- 
man soul, a thinking, immaterial being, is completely 
separated from the body, which is extended and ma- 
terial. Yet it is united to the body at a certain point 
in the brain (the glandula pinealis) for the purpose of 
receiving impressions from the outer world and effecting 
muscular movements. The animals, not being en- 
dowed with thought, have no soul : they are mere auto- 
mata, or cleverly constructed machines, whose sensa- 
tions, presentations, and volitions are purely mechan- 
ical, and take place according to the ordinary laws of 
physics. Hence Descartes was a dualist in human 
psychology, and a monist in the psychology of the 
brute. This open contradiction in so clear and acute 
a thinker is very striking; in explaning it, it is not 
unnatural to suppose that he concealed his real opin- 
ion, and left the discovery of it to independent scholars. 
As a pupil of the Jesuits, Descartes had been taught to 
deny the truth in the face of his better insight; and 
perhaps he dreaded the power and the fires of the 
Church. Besides, his sceptical principle, that every 
sincere effort to attain the truth must start with a doubt 
of the traditional dogma had already drawn upon him 
fanatical accusations of scepticism and atheism. The 
great influence which Descartes had on subsequent 

13 173 


philosophy was very remarkable, and entirely in har- 
mony with his "book-keeping by double entry." The 
materialists of the seventeenth and eighteenth centuries 
appealed to the Cartesian theory of the animal soul and 
its purely mechanical activity in support of their mon- 
istic psychology. The spiritualists, on the other hand, 
asserted that their dogma of the immortality of the soul 
and its independence of the body was firmly established 
by Descartes' theory of the human soul. This view 
is still prevalent in the camp of the theologians and 
dualistic metaphysicians. The scientific conception 
of nature, however, which has been built up in the 
nineteenth century, has, with the aid of empirical prog- 
ress, in physiological and comparative psychology, 
completely falsified it. 

II. Neurological theory of consciousness. It is pres- 
ent only in man and those higher animals which have 
a centralized nervous system and organs of sense. 
The conviction that a large number of animals at 
least the higher mammals are not less endowed than 
man with a thinking soul and consciousness prevails 
in modern zoology, exact physiology, and the monistic 
psychology. The immense progress we have made 
in the various branches of biology has contributed to 
bring about a recognition of this important truth. 
We confine ourselves for the present to the higher ver- 
tebrates, and especially the mammals. That these 
most intelligent specimens of these highly developed 
vertebrates apes and dogs, in particular have a 
strong resemblance to man in their whole psychic 
life has been recognized and speculated on for thou- 
sands of years. Their faculty of presentation and 
sensation, of feeling and desire, is so like that of man 
that we need adduce no proof of our thesis. But even 


the higher associational activity of the brain, the for- 
mation of judgments and their connection into chains 
of reasoning, thought, and consciousness in the nar- 
rower sense, are developed in them after the same fash- 
ion as in man : they differ only in degree, not in kind. 
Moreover, we learn from comparative anatomy and his- 
tology that the intricate structure of the brain (both in 
general and in detail) is substantially the same in the 
mammals as it is in man. The same lesson is enforced 
by comparative ontogeny with regard to the origin of 
these psychic organs. Comparative physiology teaches 
us that the various states of consciousness are just 
the same in these highest placentals as in man; and 
we learn by experiment that there is the same reaction 
to external stimuli. The higher animals can be nar- 
cotized by alcohol, chloroform, ether, etc., and may be 
hypnotized by the usual methods, just as in the case of 

It is, however, impossible to determine mathemati- 
cally at what stage of animal life consciousness is to be 
first recognized as such. Some zoologists draw the line 
very high in the scale, others very low. Darwin, who 
most accurately distinguishes the various stages of 
consciousness, intelligence, and emotion in the higher 
animals, and explains them by progressive evolution, 
points out how difficult, or even impossible, it is to de- 
termine the first beginning of this supreme psychic fac- 
ulty in the lower animals. Personally, out of the many 
contradictory theories, I take that to be most probable 
which holds the centralization of the nervous system to 
be a condition of consciousness ; and that is wanting in 
the lower classes of animals. The presence of a central 
nervous organ, of highly developed sense-organs, and 
an elaborate association of groups of presentations, 


seem to me to be required before the unity of conscious- 
ness is possible. 

III. Animal theory of consciousness. All animals, 
arid they alone, have consciousness. This theory 
would draw a sharp distinction between the psychic 
life of the animal and of the plant. Such a distinc- 
tion was urged by many of the older writers, and was 
clearly formulated by Linn6 in his celebrated Sy sterna 
Naturae ; the two great kingdoms of the organic world 
are, in his opinion, divided by the fact that animals 
have sensation and consciousness, and the plants are 
devoid of them. Later on Schopenhauer laid stress on 
the same distinction : " Consciousness is only known 
to us as a feature of animal nature. Even though it 
extend upwards through the whole animal kingdom, 
even to man and his reason, the unconsciousness of the 
plant, from which it started, remains as the basic feat- 
ure. In the lowest animals we have but the dawn of 
it." The inaccuracy of this view was obvious by about 
the middle of the present century, when a deeper study 
was made of the psychic activity of the lower animal 
forms, especially the ccelenterates (sponges and cni- 
daria) : they are undoubtedly animals, yet there is no 
more trace of a definite consciousness in them than in 
most of the plants. The distinction between the two 
kingdoms was still further obliterated when more care- 
ful research was made into their unicellular forms. 
There is no psychological difference between the plas- 
mophagous protozoa and the plasmodomous proto- 
phyta, even in respect of their consciousness. 

IV. Biological theory of consciousness. It is found 
in all organisms, animal or vegetal, but not in lifeless 
bodies (such as crystals). This opinion is usually as- 
sociated with the idea that all organisms (as distin- 


guished from inorganic substances) have souls: the 
three ideas life, soul, and consciousness are then 
taken to be coextensive. Another modification of this 
view holds that, though these fundamental phenomena 
of organic life are inseparably connected, yet conscious- 
ness is only a part of the activity of the soul, and of the 
vital activity. Fechner, in particular, has endeavored 
to prove that the plant has a " soul/' in the same sense 
as an animal is said to have one ; and many credit the 
vegetal soul with a consciousness similar to that of 
the animal soul. In truth, the remarkable stimulated 
movements of the leaves of the sensitive plants (the mi- 
mosa, drosera, and dionaea), the automatic movements 
of other plants (the clover and wood-sorrel, and espe- 
cially the hedysarum), the movements of the "sleeping 
plants " (particularly the papilionacea) , etc., are strik- 
ingly similar to the movements of the lower animal 
forms: whoever ascribes consciousness to the latter 
cannot refuse it to such vegetal forms. 

V. Cellular theory of consciousness. It is a vital prop- 
erty of every cell. The application of the cellular the- 
ory to every branch of biology involved its extension 
to psychology. Just as we take the living cell to be 
the * elementary organism " in anatomy and physiolo- 
gy, and derive the whole system of the multicellular 
animal or plant from it, so, with equal right, we may 
consider the "cell-soul" to be the psychological unit, 
and the complex psychic activity of the higher organism 
to be the result of the combination of the psychic activ- 
ity of the cells which compose it. I gave the outlines 
of this cellular psychology in my General Morphology 
in 1866, and entered more fully into the subject in my 
paper on "Cell-Souls and Soul-Cells." I was led to a 
deeper study of this " elementary psychology " by my 



protracted research into the unicellular forms of life. 
Many of these tiny (generally microscopic) protists 
show similar expressions of sensation and will, and 
similar instincts and movements, to those of higher 
animals ; that is especially true of the very sensitive 
and lively infusoria. In the relation of these sensitive 
cell-organisms to their environment, and in many other 
of their vital expressions (for instance, in the wonder- 
ful architecture of the rhizopods, the thalamophorae, 
and the infusoria), we seemed to have clear indications 
of conscious psychic action. If, then, we accept the 
biological theory of consciousness (No. IV.), and credit 
every psychic function with a share of that faculty, we 
shall be compelled to ascribe it to each independent pro- 
tist cell. In that case its material basis would be either 
the entire protoplasm of the cell, or its nucleus, or a por- 
tion of it. In the " psychade theory " of Fritz Schultze 
the elementary consciousness of the psychade would 
have the same relation to the individual cells as per- 
sonal consciousness has to the multicellular organism 
of the personality in the higher animals and man. 
It is impossible definitively to disprove this theory, 
which I held at one time. Still, I now feel compelled 
to agree with Max Verworn, in his belief that none of 
the protists have a developed self-consciousness, but 
that their sensations and movements are of an uncon- 
scious character. 

VI. Atomistic theory of consciousness, It is an ele- 
mentary property of all atoms. This atomistic hy- 
pothesis goes furthest of all the different views as to 
the extension of consciousness. It certainly escapes 
the difficulty which so many philosophers and biolo- 
gists experience in solving the problem of the first or- 
igin of consciousness. It is a phenomenon of so pecu- 


liar a character that a derivation of it from other psy- 
chic functions seems extremely hazardous. It seemed, 
therefore, the easiest way out of the difficulty to con- 
ceive it as an inherent property of all matter, like gravi- 
tation or chemical affinity. On that hypothesis there 
would be as many forms of this original consciousness 
as there are chemical elements ; each atom of hydrogen 
would have its hydrogenic consciousness, each atom 
of carbon its carbonic consciousness, and so forth. 
There are philosophers, even, who ascribe conscious- 
ness to the four elements of Empedocles, the union of 
which, by "love and hate," produces the totality of 

Personally, I have never subscribed to this hypoth- 
esis of atomic consciousness. I emphasize the point 
because Emil du Bois-Reymond has attributed it to 
me. In the-controversy I had with him (1880) he vio- 
lently attacked my " pernicious and false philosophy," 
and contended that I had, in my paper on " The Peri- 
genesis of the Plastidule," " laid it down as a meta- 
physical axiom that every atom has its individual con- 
sciousness." On the contrary, I explicitly stated that I 
conceive the elementary psychic qualities of sensation 
and will, which may be attributed to atoms, to be un- 
conscious just as unconscious as the elementary mem- 
ory which I, in company with that distinguished physi- 
ologist, Ewald Hering, consider to be " a common func- 
tion of all organized matter " or, more correctly, * liv- 
ing substance." Du Bois-Reymond curiously confuses 
" soul " and " consciousness " ; whether from oversight 
or not I cannot say. Since he considers consciousness 
to be a transcendental phenomenon (as we shall see 
presently), while denying that character to other psy 
chic functions the action of the senses, for example I 



must infer that he recognizes the difference of the two 
ideas. Other parts of his eloquent speeches contain 
quite the opposite view, for the famous orator not in- 
frequently contradicts himself on important questions 
of principle. However, I repeat that, in my opinion, 
consciousness is only part of the psychic phenomena 
which we find in man and the higher animals; the 
great majority of them are unconscious. 

However divergent are the different views as to the 
nature and origin of consciousness, they may, never- 
theless, on a clear and logical examination, all be re- 
duced to two fundamental theories the transcenden- 
tal (or dualistic) and the physiological (or monistic). 
I have myself always held the latter view, in the light 
of my evolutionary principles, and it is now shared by 
a great number of distinguished scientists, though it 
is by no means generally accepted. The transcenden- 
tal theory is the older and much more common ; it has 
recently come once more into prominence, principally 
through Du Bois-Reymond, and it has acquired a great 
importance in modern discussions of cosmic problems 
through his famous "Ignorabimus speech." On ac- 
count of the extreme importance of this fundamental 
question we must touch briefly on its main features. 

In the celebrated discourse on " The Limits of Nat- 
ural Science," which E. du Bois-Reymond gave on 
August 14, 1872, at the Scientific Congress at Leipzig, 
he spoke of two "absolute limits" to our possible 
knowledge of nature which the human mind will never 
transcend in its most advanced science never, as the 
oft-quoted termination of the address, " Ignorabimus," 
emphatically pronounces. The first absolutely in- 
soluble "world-enigma" is the "connection of matter 
and force," and the distinctive character of these fun- 



damental natural phenomena ; we shall go more fully 
into this" problem of substance" in the twelfth chap- 
ter. The second insuperable difficulty of philosophy is 
given as the problem of consciousness the question 
how our mental activity is to be explained by material 
conditions, especially movements, how " substance [the 
substance which underlies matter and force] comes, 
under certain conditions, to feel, to desire, and to think." 

For brevity, and in order to give a characteristic 
name to the Leipzig discourse, I have called it the " Ig- 
norabimus speech " ; this is the more permissible, as 
E. du Bois-Reymond himself, with a just pride, eight 
years afterwards, speaking of the extraordinary con- 
sequences of his discourse, said : " Criticism sounded 
every possible note, from friendly praise to the severest 
censure, and the word ' Ignorabimus/ which was the 
culmination of my inquiry, was at once transformed 
into a kind of scientific shibboleth." It is quite true 
that loud praise and approbation resounded in the halls 
of the dualistic and spiritualistic philosophy, and es- 
pecially in the camp of the " Church militant " ; even 
the spiritists and the host of believers, who thought 
the immortality of their precious souls was saved by 
the "Ignorabimus," joined in the chorus. The "se- 
verest censure " came at first only from a few scientists 
and philosophers from the few who had sufficient 
scientific knowledge and moral courage to oppose the 
dogmatism of the all-powerful secretary and dictator 
of the Berlin Academy of Science. 

Towards the end, however, the author of the " Igno- 
rabimus speech " briefly alluded to the question wheth- 
er these two great "world-enigmas," the general prob- 
lem of substance and the special problem of conscious- 
ness., are not two aspects of one and the same problem. 



" This idea" he said, " is certainly the simplest, and 
preferable to the one which makes the world doubly 
incomprehensible. Such, however, is the nature of 
things that even here we can obtain no clear knowl- 
edge, and it is useless to speak further of the question." 
The latter sentiment I have always stoutly contested, 
and have endeavored to prove that the two great ques- 
tions are not two distinct problems. " The neuro- 
logical problem of consciousness is but a particular 
aspect of the all -pervading cosmological problem of 

The peculiar phenomenon of consciousness is not, 
as Du Bois-Reymond and the dualistic school would 
have us believe, a completely " transcendental " prob- 
lem ; it is, as I showed thirty-three years ago, a phys- 
iological problem, and, as such, must be reduced to 
the phenomena of physics and chemistry. I subse- 
quently gave it the more definite title of a neurologi- 
cal problem, as I share the view that true conscious- 
ness (thought and reason) is only present in those 
higher animals which have a centralized nervous sys- 
tem and organs of sense of a certain degree of devel- 
opment. Those conditions are certainly found in the 
higher vertebrates, especially in the placental mam- 
mals, the class from which man has sprung. The 
consciousness of the highest apes, dogs, elephants, etc., 
differs from that of man in degree only, not in kind, 
and the graduated interval between the consciousness 
of these "rational" placentals and that of the lowest 
races of men (the Veddahs, etc.) is less than the corre- 
sponding interval between these uncivilized races and 
the highest specimens of thoughtful humanity (Spi- 
noza, Goethe, Lamarck, Darwin, etc.). Consciousness 
is but a part of the higher activity of the soul, and as 



such it is dependent on the normal structure of the cor- 
responding psychic organ, the brain. 

Physiological observation and experiment determined 
twenty years ago that the particular portion of the 
mammal-brain which we call the seat (preferably the 
organ) of consciousness is a part of the cerebrum, an 
area in the late-developed gray bed, or cortex, which is 
evolved out of the convex dorsal portion of the primary 
cerebral vesicle, the " fore-brain." Now, the morpho- 
logical proof of this physiological thesis has been suc- 
cessfully given by the remarkable progress of the mi- 
croscopic anatomy of the brain, which we owe to the 
perfect methods of research of modern science (Kolliker, 
Flechsig, Golgi, Edinger, Weigert, and others). 

The most important development is the discovery of 
the organs of thought by Paul Flechsig, of Leipzig ; he 
proved that in the gray bed of the brain are found the 
four seats of the central sense-organs, or four "inner 
spheres of sensation " the sphere of touch in the ver- 
tical lobe, the sphere of smell in the frontal lobe, the 
sphere of sight in the occipital lobe, and the sphere of 
hearing in the temporal lobe. Between these four 
" sense-centres " lie the four great " thought-centres," 
or centres of association, the real organs of mental life ; 
they are those highest instruments of psychic activity 
that produce thought and consciousness. In front we 
have the frontal brain or centre of association ; behind, 
on top there is the vertical brain, or parietal centre of 
association, and underneath the principal brain, or 
" the great occipito-temporal centre of association " 
(the most important of all) ; lower down, and inter- 
nally, the insular brain or the insula of Reil, the insular 
centre of association. These four " thought-centres," 
distinguished from the intermediate " sense-centres " 



by a peculiar and elaborate nerve-structure, are the 
true and sole organs of thought and consciousness. 
Flechsig has recently pointed out that, in the case of 
man, very specific structures are found in one part of 
them ; these structures are wanting in the other mam- 
mals, and they, therefore, afford an explanation of the 
superiority of man's mental powers. 

The momentous announcement of modern physiol- 
ogy, that the cerebrum is the organ of consciousness 
and mental action in man and the higher mammals, 
is illustrated and confirmed by the pathological study 
of its diseases. When parts of the cortex are destroyed 
by disease their respective functions are affected, and 
thus we are enabled, to some extent, to localize the ac- 
tivities of the brain ; when certain parts of the area are 
diseased, that portion of thought and consciousness 
disappears which depends on those particular sections. 
Pathological experiment yields the same result; the 
decay of some known area (for instance, the centre of 
speech) extinguishes its function (speech). In fact, 
there is proof enough in the most familiar phenomena 
of consciousness of their complete dependence on chem- 
ical changes in the substance of the brain. Many bev- 
erages (such as coffee and tea) stimulate our powers of 
thought ; others (such as wine and beer) intensify feel- 
ing; musk and camphor reanimate the fainting con- 
sciousness; ether and chloroform deaden it, and so 
forth. How would that be possible if consciousness 
were an immaterial entity, independent of these ana- 
tomical organs? And what becomes of the conscious- 
ness of the " immortal soul " when it no longer has the 
use of these organs? 

These and other familiar facts prove that man's con- 
sciousness and that of the nearest mammals is 



changeable, and that its activity is always open to 
modification from inner (alimentation, circulation, etc.) 
and outer causes (lesion of the brain, stimulation, etc.). 
Very instructive, too, are the facts of double and in- 
termittent consciousness, which remind us of " alter- 
nate generations of presentations." The same indi- 
vidual has an entirely different consciousness on dif- 
ferent days, with a change of circumstances ; he does 
not know to-day what he did yesterday : yesterday he 
could say, " I am I " ; to-day he must say, " I am an- 
other being." Such intermittence of consciousness 
may last not only days, but months, and even years; 
the change may even become permanent. 

As everybody knows, the new-born infant has no 
consciousness. Preyer has shown that it is only de- 
veloped after the child has begun to speak ; for a long 
time it speaks of itself in the third person. In the im- 
portant moment when it first pronounces the word " I," 
when the feeling of self becomes clear, we have the be- 
ginning of self-consciousness, and of the antithesis to 
the non-ego. The rapid and solid progress in knowl- 
edge which the child makes in its first ten years, under 
the care of parents and teachers, and the slower progress 
of the second decade, until it reaches complete maturity 
of mind, are intimately connected with a great advance- 
ment in the growth and development of consciousness 
and of its organ, the brain. But even when the pupil 
has got his " certificate of maturity " his consciousness 
is still far from mature ; it is then that his " world- 
consciousness " first begins to develop, in his manifold 
relations with the outer world. Then, in the third dec- 
ade, we have the full maturity of rational thought and 
consciousness, which, in cases of normal development, 
yield their ripe fruits during the next three decades. 



The slow, gradual degeneration of the higher mental 
powers, which characterizes senility, usually sets in at 
the commencement of the seventh decade sometimes 
earlier, sometimes later. Memory, receptiveness, and 
interest in particular objects gradually decay; though 
productivity, mature consciousness, and philosophic^ 
interest in general truths often remain for many years 

The individual development of consciousness in ear- 
lier youth proves the universal validity of the biogenetic 
law ; and, indeed, it is still recognizable in many ways 
during the later years. In any case, the ontogenesis 
of consciousness makes it perfectly clear that it is not 
an " immaterial entity," but a physiological function 
of the brain, and that it is, consequently, no exception 
to the general law of substance. 

From the fact that consciousness, like all other psy- 
chic functions, is dependent on the normal development 
of certain organs, and that it gradually unfolds in 
the child in proportion to the development of those 
organs, we may already conclude that it has arisen 
in the animal kingdom by a gradual historical de- 
velopment. Still, however certain we are of the fact 
of this natural evolution of consciousness, we are, un- 
fortunately, not yet in a position to enter more deeply 
into the question and construct special hypotheses in 
elucidation of it. Palaeontology, it is true, gives us a 
few facts which are not without significance. For in- 
stance, the quantitative and qualitative development 
of the brain of the placental mammals during the Ter- 
tiary period is very remarkable. The cavity of many 
of the fossil skulls of the period has been carefully ex- 
amined, and has given us a good deal of reliable infor- 
mation as to the size, and, to some extent, as to the 



structure, of the brain they enclosed. We find, within 
the limits of one and the same group (the ungulates, 
the rodents, or the primates), a marked advance in the 
later miocene and pliocene specimens as compared with 
the earlier eocene and oligocene representatives of the 
same stem; in the former the brain (in proportion to 
the size of the organism) is six to eight times as large 
as in the latter. 

Moreover, that highest stage of consciousness, which 
is reached by man alone, has been evolved step by 
step even by the very progress of civilization from 
a lower condition, as we find illustrated to-day in the 
case of uncivilized races. That is easily proved by a 
comparison of their languages, which is closely con- 
nected with the comparison of their ideas. The higher 
the conceptual faculty advances in thoughtful civil- 
ized man, the more qualified he is to detect common 
features amid a multitude of details, and embody them 
in general concepts, and so much the clearer and 
deeper does his consciousness become. 


The Citadel of Superstition Athanatism and Thanatism Indi- 
vidual Character of Death Immortality of the Unicellular 
Organisms (Protists) Cosmic and Personal Immortality 
Primary Thanatism (of Uncivilized Peoples) Secondary 
Thanatism (of Ancient and Recent Philosophers) Athan- 
atism and Religion Origin of the Belief in Immortality 
Christian Athanatism Eternal Life The Day of Judgment 
Metaphysical Athanatism Substance of the Soul Ether 
Souls and Air Souls ; Fluid Souls and Solid Souls Immor- 
tality of the Animal Soul Arguments for and Against Athan- 
atism A th anatist Illusions . 

\17HEN we turn from the genetic study of the soul 
' * to the great question of its immortality, we come 
to that highest point of superstition which is regarded 
as the impregnable citadel of all mystical and dual- 
istic notions. For in this crucial question, more than 
in any other problem, philosophic thought is compli- 
cated by the selfish interest of the human personality, 
who is determined to have a guarantee of his existence 
beyond the grave at any price. This "higher neces- 
sity of feeling " is so powerful that it sweeps aside all 
the logical arguments of critical reason. Consciously 
or unconsciously, most men are influenced in all their 
general views, and, therefore, in their theory of life, by 
the dogma of personal immortality ; and to this theo- 
retical error must be added practical consequences of 

1 88 


the most far-reaching character. It is our task, there- 
fore, to submit every aspect of this important dogma to 
a critical examination, and to prove its untenability in 
the light of the empirical data of modern biology. 

In order to have a short and convenient expression 
for the two opposed opinions on the question, we shall 
call the belief in man's personal immortality " athan- 
atism" (from athanes or athanatos = immortal). On 
the other hand, we give the name of "thanatism" 
(from thanatos = death) to the opinion which holds 
that at a man's death not only all the other physiologi- 
cal functions are arrested, but his " soul " also disap- 
pears that is, that sum of cerebral functions which 
psychic dualism regards as a peculiar entity, inde- 
pendent of the other vital processes in the living body. 

In approaching this physiological problem of death 
we must point out the individual character of this or- 
ganic phenomenon. By death we understand simply 
the definitive cessation of the vital activity of the indi- 
vidual organism, no matter to which category or stage 
of individuality the organism in question belongs. 
Man is dead when his own personality ceases to exist, 
whether he has left offspring that they may continue 
to propagate for many generations or not. In a cer- 
tain sense we often say that the minds of great men 
(in a dynasty of eminent rulers, for instance, or a fam- 
ily of talented artists) live for many generations ; and 
in the same way we speak of the "soul" of a noble 
woman living in her children and children's children. 
But in these cases we are dealing with intricate phe- 
nomena of heredity, in which a microscopic cell (the 
sperm-cell of the father or the egg-cell of the mother) 
transmits certain features to offspring. The particu- 
lar personalities who produce those sexual cells in thou- 
4 189 


sands are mortal beings, and at their death their per- 
sonal psychic activity is extinguished like every other 
physiological function. 

A number of eminent zoologists Weismann being 
particularly prominent have recently defended the 
opinion that only the lowest unicellular organisms, 
the protists, are immortal, in contradistinction to the 
multicellular plants and animals, whose bodies are 
formed of tissues. This curious theory is especially 
based on the fact that most of the protists multiply 
without sexual means, by division or the formation of 
spores. In such processes the whole body of the 
unicellular organism breaks up into two or more 
equal parts (daughter cells), and each of these portions 
completes itself by further growth until it has the 
size and form of the mother cell. However, by the 
very process of division the individuality of the 
unicellular creature has been destroyed ; both its 
physiological and its morphological unity have gone. 
The view of Weismann is logically inconsistent with 
the very notion of individual an "indivisible" en- 
tity ; for it implies a unity which cannot be divided 
without destroying its nature. In this sense the 
unicellular protophyta and protozoa are throughout 
life physiological individuals, just as much as the 
multicellular tissue-plants and animals. A sexual 
propagation by simple division is found in many of 
the multicellular species (for instance, in many 
cnidaria, corals, medusae, etc.); the mother animal, 
the division of which gives birth to the two daugh- 
ter animals, ceases to exist with the segmentation. 
" The protozoa," says Weismann, " have no indi- 
viduals and no generations in the matazoic sense." 
I must entirely dissent from his thesis. As I was 



the first to introduce the title of metazoa, and oppose 
these multicellular, tissue-forming animals to the uni- 
cellular protozoa (infusoria, rhizopods, etc.), and as 
I was the first to point out the essential difference in 
the development of the two (the former from germinal 
layers, and the latter not), I must protest that I con- 
sider the protozoa to be just as mortal in the physio- 
logical (and psychological) sense as the metazoa ; nei- 
ther body .nor soul is immortal in either group. The 
other erroneous consequences of Weismann's notion 
have been refuted by Moebius (1884), who justly re- 
marks that " every event in the world is periodic," and 
that " there is no source from which immortal organic 
individuals might have sprung." 

When we take the idea of immortality in the widest 
sense, and extend it to the totality of the knowable uni- 
verse, it has a scientific significance; it is then not 
merely acceptable, but self - evident, to the monistic 
philosopher. In that sense the thesis of the indestruc- 
tibility and eternal duration of all that exists is equiva- 
lent to our supreme law of nature, the law of substance 
(see chap. xii.). As we intend to discuss this immor- 
tality of the cosmos fully later on, in establishing the 
theory of the persistence of matter and force, we shall 
not dilate on it at present. We pass on immediately 
to the criticism of that belief in immortality which is 
the only sense usually attached to the word, the im- 
mortality of the individual soul. We shall first in- 
quire into the extent and the origin of this mystic and 
dualistic notion, and point out, in particular, the wide 
acceptance of the contradictory thesis, our monistic, 
empirically established thanatism. I must distin- 
guish two essentially different forms of thanatism 
primary and secondary; primary thanatism is the 



original absence of the dogma of immortality (in the 
primitive uncivilized races) ; secondary thanatism is 
the later outcome of a rational knowledge of nature 
in the civilized intelligence. 

We still find it asserted in philosophic, and espe- 
cially in theological, works that belief in the personal 
immortality of the human soul was originally shared 
by all men or, at least, by all " rational " men. That 
is not the case. This dogma is not an original idea of 
the human mind, nor has it ever found universal ac- 
ceptance. It has been absolutely proved by modern 
comparative ethnology that many uncivilized races of 
the earliest and most primitive stage had no notion 
either of immortality or of God. That is true, for in- 
stance, of the Veddahs of Ceylon, those primitive pyg- 
mies whom, on the authority of the able studies of the 
Sarasins, we consider to be a relic of the earliest in- 
habitants of India ;* it is also the case in several of the 
earliest groups of the nearly related Dravidas, the Ind- 
ian Seelongs, and some native Australian races. Sim- 
ilarly, several of the primitive branches of the Ameri- 
can race, in the interior of Brazil, on the upper 
Amazon, etc., have no knowledge either of gods or 
immortality. This primary absence of belief in im- 
mortality and deity is an extremely important fact ; it 
is, obviously, easy to distinguish from the secondary 
absence of such belief, which has come about in the 
highest civilized races as the result of laborious critico- 
philosophical study. 

Differently from the primary thanatism which orig- 
inally characterized primitive man, and has always 
been widely spread, the secondary absence of belief 

* E. Haeckel, A Visit to Ceylon. 


in immortality is only found at a late stage of history : 
it is the ripe fruit of profound reflection on life and death, 
the outcome of bold and independent philosophical 
speculation. We first meet it in some of the Ionic phi- 
losophers of the sixth century B.C., then in the founders 
of the old materialistic philosophy, Democritus and 
Empedocles, and also in Simonides and Epicurus, Sen- 
eca and Plinius, and in an elaborate form in Lucretius 
Carus. With the spread of Christianity at the decay 
of classical antiquity, athanatism, one of its chief ar- 
ticles of faith, dominated the world, and so, amid other 
forms of superstition, the myth of personal immortal- 
ity came to be invested with a high importance. 

Naturally, through the long night of the Dark Ages 
it was rarely that a brave free-thinker ventured to ex- 
press an opinion to the contrary : the examples of Gal- 
ileo, Giordano Bruno, and other independent philos- 
ophers, effectually destroyed all freedom of utterance. 
Heresy only became possible when the Reformation 
and the Renaissance had broken the power of the pa- 
pacy. The history of modern philosophy tells of the 
manifold methods by which the matured mind of man 
sought to rid itself of the superstition of immortality. 
Still, the intimate connection of the belief with the Chris- 
tian dogma invested it with such power, even in the 
more emancipated sphere of Protestantism, that the 
majority of convinced free-thinkers kept their senti- 
ments to themselves. From time to time some dis- 
tinguished scholar ventured to make a frank declara- 
tion of his belief in the impossibility of the continued 
life of the soul after death. This was done in France 
in the second half of the eighteenth century by Vol- 
taire, Danton, Mirabeau, and others, and by the lead- 
ers of the materialistic school of those days, Holbach, 


Lamettrie, etc. The same opinion was defended by the 
able friend of the Materialists, the greatest of the Ho- 
henzoilerns, the monistic "philosopher of Sans-souci." 
What would Frederick the Great, the " crowned thana- 
tist and atheist/' say, could he compare his monistic 
views with those of his successor of to-day ? 

Among thoughtful physicians the conviction that the 
existence of the soul came to an end at death has been 
common for centuries: generally, however, they re- 
frained from giving it expression. Moreover, the em- 
pirical science of the brain remained so imperfect dur- 
ing the last century that the soul could continue to be 
regarded as its mysterious inhabitant. It was the 
gigantic progress of biology in the present century, 
and especially in the latter half of the century, that 
finally destroyed the myth. The establishment of 
the theory of descent and the cellular theory, the 
astounding discoveries of ontogeny and experimental 
physiology above all, the marvellous progress of the 
microscopic anatomy of the brain, gradually deprived 
athanativSm of every basis; now, indeed, it is rarely 
that an informed and honorable biologist is found to 
defend the immortality of the soul. All the monistic 
philosophers of the century (Strauss, Feuerbach, Buch- 
ner, Spencer, etc.) are thanatists. 
i The dogma of personal immortality owes its great 
popularity and its high importance to its intimate con- 
nection with the teaching of Christianity. This cir- 
cumstance gave rise to the erroneous and still preva- 
lent belief that the myth is a fundamental element 
of all the higher religions. That is by no means 
the case. The higher Oriental religions include no 
belief whatever in the immortality of the soul; it is 
not found in Buddhism, the religion that dominates 



thirty per cent, of the entire human race; it is not 
found in the ancient popular religion of the Chinese, 
nor in the reformed religion of Confucius which suc- 
ceeded it; and, what is still more significant, it is 
not found in the earlier and purer religion of the 
Jews. Neither in the " five Mosaic books/' nor in 
any of the writings of the Old Testament which were 
written before the Babylonian Exile, is there any 
trace of the notion of individual persistence after 

The mystic notion that the human soul will live for- 
ever after death has had a polyphyletic origin. It was 
unknown to the earliest speaking man (the hypotheti- 
cal homo primigenius of Asia), to his predecessors, of 
course, the pithecanthropus and prothylobates, and to 
the least developed of his modern successors, the Ved- 
dahs of Ceylon, the Seelongs of India, and other dis- 
tant races. With the development of reason and deep- 
er reflection on life and death, sleep and dreams, mystic 
ideas of a dualistic composition of our nature were 
evolved independently of each other in a number of 
the earlier races. Very different influences were at 
work in these polyphyletic creations worship of ances- 
tors, love of relatives, love of life and desire of its pro- 
longation, hope of better conditions of life beyond the 
grave, hope of the reward of good and punishment 
of evil deeds, and so forth. Comparative psychology 
has recently brought to our knowledge a great variety 
of myths and legends of that character; they are, for 
the most part, closely associated with the oldest forms 
of theistic and religious belief. In most of the modern 
religions athanatism is intimately connected with the- 
ism ; the majority of believers transfer their material- 
istic idea of a " personal God" to their " immortal soul," 



That is particularly true of the dominant religion of 
modern civilized states, Christianity. 

As everybody knows, the dogma of the immortality 
of the soul has long since assumed in the Christian 
religion that rigid form which it has in the articles of 
faith : " I believe in the resurrection of the body and 
in an eternal life." Man will arise on " the last day," 
as Christ is alleged to have done on Easter morn, and 
receive a reward according to the tenor of his earthly 
life. This typically Christian idea is thoroughly ma- 
terialistic and anthropomorphic ; it is very little supe- 
rior to the corresponding crude legends of uncivilized 
peoples. The impossibility of " the resurrection of the 
body " is clear to every man who has some knowledge 
of anatomy and physiology. The resurrection of Christ, 
which is celebrated every Easter by millions of Chris- 
tians, is as purely mythical as " the awakening of the 
dead," which he is alleged to have taught. These mystic 
articles of faith are just as untenable in the light of 
pure reason as the cognate hypothesis of " eternal life." 

The fantastic notions which the Christian Church 
disseminates as to the eternal life of the immortal soul 
after the dissolution of the body are just as material- 
istic as the dogma of "the resurrection of the body." 
In his interesting work on Religion in the Light of the 
Darwinian Theory, Savage justly remarks : " It is one 
of the standing charges of the Church against science 
that it is materialistic. I must say, in passing, that 
the whole ecclesiastical dortrine of a future life has al- 
ways been, and still is, materialism of the purest type. 
It teaches that the material body shall rise, and dwell 
in a material heaven." To prove this one has only to 
read impartially some of the sermons and ornate dis- 
courses in which the glory of the future life is extolled 



as the highest good of the Christian, and belief in it is 
laid down to be the foundation of morality. According 
to them, all the joys of the most advanced modern civ- 
ilization await the pious believer in Paradise, while 
the "All-loving Father " reserves his eternal fires for 
the godless materialist. 

In opposition to the materialist athanatism, which is 
dominant in the Christian and Mohammedan Churches, 
we have, apparently, a purer and higher form of faith 
in the metaphysical athanatism, as taught by most of 
our dualist and spiritualist philosophers. Plato must 
be considered its chief creator: in the fourth century 
before Christ he taught that complete dualism of body 
and soul which afterwards became one of the most im- 
portant, theoretically, and one of the most influential, 
practically, of the Christian articles of faith. The body 
is mortal, material, physical; the soul is immortal, 
immaterial, metaphysical. They are only temporarily 
associated, for the course of the individual life. As 
Plato postulated an eternal life before as well as after 
this temporary association, he must be classed as an 
adherent of " metempsychosis/' or transmigration of 
souls ; the soul existed as such, or as an " eternal idea," 
before it entered into a human body. When it quits 
one body it seeks such other as is most suited to its 
character for its habitation. The souls of bloody ty- 
rants pass into the bodies of wolves and vultures, those 
of virtuous toilers migrate into the bodies of bees and 
ants, and so forth. The childish naivety of this Pla- 
tonic morality is obvious; on closer examination his 
views are found to be absolutely incompatible with the 
scientific truth which we owe to modern anatomy, 
physiology, histology, and ontogeny; we mention 
them only because, in spite of their absurdity, they 



have had a profound influence on thought and culture. 
On the one hand, the mysticism of the Neo-Platonists, 
which penetrated into Christianity, attaches itself to 
the psychology of Plato ; on the other hand, it became 
subsequently one of the chief supports of spiritualistic 
and idealistic philosophy. The Platonic " idea " gave 
way in time to the notion of psychic " substance"; this 
is just as incomprehensible and metaphysical, though 
it often assumed a physical appearance. 

The conception of the soul as a " substance" is far 
from clear in many psychologists; sometimes it is re- 
garded as an " immaterial " entity of a peculiar charac- 
ter in an abstract and idealistic sense, sometimes in a 
concrete and realistic sense, and sometimes as a con- 
fused tertium quid between the two. If we adhere to 
the monistic idea of substance, which we develop in 
chap, xii., and which takes it to be the simplest element 
of our whole world-system, we find energy and matter 
inseparably associated in it. We must, therefore, dis- 
tinguish in the " substance of the soul " the character- 
istic psychic energy which is all we perceive (sensation, 
presentation, volition, etc.), and the psychic matter, 
which is the inseparable basis of its activity that is, 
the living protoplasm. Thus, in the higher animals 
the " matter " of the soul is a part of the nervous sys- 
tem ; in the lower nerveless animals and plants it is a 
part of their multicellular protoplasmic body; and in 
the unicellular protists it is a part of their protoplasmic 
cell-body. In this way we are brought once more to 
the psychic organs, and to an appreciation of the fact 
that these material organs are indispensable for the 
action of the soul; but the soul itself is actual it is 
the sum-total of their physiological functions. 

However, the idea of a specific " soul - substance " 


found in the dualistic philosophers who admit such 
a thing is very different from this. They conceive 
the immortal soul to be material, yet invisible, and 
essentially different from the visible body which it 

Thus invisibility comes to be regarded as a most im- 
portant attribute of the soul. Some, in fact, compare 
the soul with ether, and regard it, like ether, as an ex- 
tremely subtle, light, and highly elastic material, an 
imponderable agency, that fills the intervals between 
the ponderable particles of the living organism, others 
compare the soul with the wind, and so give it a gas- 
eous nature; and it is this simile which first found 
favor with primitive peoples, and led in time to the fa- 
miliar dualistic conception. When a man died, the 
body remained as a lifeless corpse, but the immortal 
soul " flew out of it with the last breath." 

The comparison of the human soul with physical 
ether as a qualitatively similar idea has assumed a 
more concrete shape in recent times through the great 
progress of optics and electricity (especially in the last 
decade) ; for these sciences have taught us a good deal 
about the energy of ether, and enabled us to formulate 
certain conclusions as to the material character of this 
all-pervading agency. As I intend to describe these 
important discoveries later on (in chap, xii.), I shall do 
no more at present than briefly point out that they ren- 
der the notion of an * etheric soul " absolutely untena- 
ble. Such an etheric soul that is a psychic sub- 
stance which is similar to physical ether, and which, 
like ether, passes between the ponderable elements of 
the living protoplasm or the molecules of the brain, 
cannot possibly account for the individual life of the 
soul. Neither the mystic notions of that kind which 



were warmly discussed about the middle of the century, 
nor the attempts of modern " Neovitalists" to put theii 
mystical " vital force " on a line with physical ether, 
call for refutation any longer. 

Much more widespread, and still much respected, is 
the view which ascribes a gaseous nature to the sub- 
stance of the soul. The comparison of human breath 
with the wind is a very old one; they were originally 
considered to be identical, and were both given the 
same name. The anemos and psyche of the Greeks, 
and the anima and spiritus of the Romans, were origi- 
nally all names for " a breath of wind " ; they were trans- 
ferred from this to the breath of man. After a time 
this " living breath " was identified with the " vital 
force," and finally it came to be regarded as the soul 
itself, or, in a narrower sense, as its highest manifes- 
tation, the " spirit." From that the imagination went 
on to derive the mystic notion of individual " spirits"; 
these, also, are still usually conceived as "aeriform 
beings " though they are credited with the physio- 
logical functions of an organism, and they have been 
photographed in certain well-known spiritist circles. 

Experimental physics has succeeded, during the 
last decade of the century, in reducing all gaseous 
bodies to a liquid most of them, also, to a solid con- 
dition. Nothing more is needed than special appara- 
tus, which exerts a violent pressure on the gases at a 
very low temperature. By this process not only the 
atmospheric elements, oxygen, hydrogen, and nitro- 
gen, but even compound gases (such as carbonic-acid 
gas) and gaseous aggregates (like the atmosphere) 
have been changed from gaseous to liquid form. In 
this way the " invisible " substances have become " vis- 
ible " to all, and in a certain sense " tangible." With 



this transformation the mystic nimbus which formerly 
veiled the character of the gas in popular estimation 
as an invisible body that wrought visible effects has 
entirely disappeared. If, then, the substance of the 
soul were really gaseous, it should be possible to liquefy 
it by the application of a high pressure at a low tem- 
perature. We could then catch the soul as it is " breathed 
out " at the moment of death, condense it, and exhibit 
it in a bottle as "immortal fluid " (Fluidum animae 
immortale). By a further lowering of temperature 
and increase of pressure it might be possible to solidify 
it to produce " soul-snow. " The experiment has not 
yet succeeded. 

If athanatism were true, if, indeed, the human soul 
were to live for all eternity, we should have to grant 
the same privilege to the souls of the higher animals, 
at least to those of the nearest related mammals (apes, 
dogs, etc.). For man is not distinguished from them 
by a special kind of soul, or by any peculiar and ex- 
clusive psychic function, but only by a higher de- 
gree of psychic activity, a superior stage of develop- 
ment. In particular, consciousness the function of 
the association of ideas, thought, and reason has 
reached a higher level in many men (by no means in 
all) than in most of the animals. Yet this difference 
is far from being so great as is popularly supposed; 
and it is much slighter in every respect than the cor- 
responding difference between the higher and the low- 
er animal souls, or even the difference between the 
highest and the lowest stages of the human soul itself. 
If we ascribe " personal immortality " to man, we are 
bound to grant it also to the higher animals. 

It is, therefore, quite natural that we should find 
this belief in the immortality of the animal soul among 



many ancient and modern peoples ; we even meet it 
sometimes to-day in many thoughtful men who pos- 
tulate an " immortal life " for themselves, and have, 
at the same time, a thorough empirical knowledge of 
the psychic life of the animals. I once knew an old 
head-forester, who, being left a widower and without 
children at an early age, had lived alone for more than 
thirty years in a noble forest of East Prussia. His 
only companions were one or two servants, with whom 
he exchanged merely a few necessary words, and a 
great pack of different kinds of dogs, with which he 
lived in perfect psychic communion. Through many 
years of training this keen observer and friend of nat- 
ure had penetrated deep into the individual souls of 
his dogs, and he was as convinced of their personal 
immortality as he was of his own. Some of his most 
intelligent dogs were, in his impartial and objective 
estimation, at a higher stage of psychic development 
than his old, stupid maid and the rough, wrinkled man- 
servant. Any unprejudiced observer, who will study 
the conscious and intelligent psychic activity of a fine 
dog for a year, and follow attentively the physiological 
processes of its thought, judgment, and reason, will 
have to admit that it has just as valid a claim to im- 
mortality as man himself. 

The proofs of the immortality of the soul, which have 
been adduced for the last two thousand years, and are, 
indeed, still credited with some validity, have their or- 
igin, for the most part, not in an effort to discover the 
truth, but in an alleged "necessity of emotion " that 
is, in imagination and poetic conceit. As Kant puts 
it, the immortality of the soul is not an object of pure 
reason, but a " postulate of practical reason.* But we 
must set " practical reason n entirely aside, together 



with all the " exigencies of emotion, or of moral educa- 
tion, etc.," when we enter upon an honest and impar- 
tial pursuit of truth ; for we shall only attain it by the 
work of pure reason, starting from empirical data and 
capable of logical analysis. We have to say the same 
of athanatism as of theism; both are creations of 
poetic mysticism and of transcendental " faith/' not of 
rational science. 

When we come to analyze all the different proofs that 
have been urged for the immortality of the soul, we find 
that not a single one of them is of a scientific character ; 
not a single one is consistent with the truths we have 
learned in the last few decades from physiological psy- 
chology and the theory of descent. The theological 
proof that a personal creator has breathed an immor- 
tal soul (generally regarded as a portion of the divine 
soul) into man is a pure myth. The cosmological 
proof that the " moral order of the world " demands 
the eternal duration of the human soul is a baseless 
dogma. The ideological proof that the " higher des- 
tiny " of man involves the perfecting of his defective, 
earthly soul beyond the grave rests on a false an- 
thropism. The moral proof that the defects and the 
unsatisfied desires of earthly existence must be fulfilled 
by " compensative justice " on the other side of eternity 
is nothing more than a pious wish. The ethnological 
proof that the belief in immortality, like the belief in 
God, is an innate truth, common to all humanity is 
an error in fact. The ontological proof that the soul, 
being a " simple, immaterial, and indivisible entity," 
cannot be involved in the corruption of death is based 
on an entirely erroneous view of the psychic phenom- 
ena; it is a spiritualistic fallacy. All these and sim- 
ilar " proofs of athanatism " are in a parlous condition ; 



they are definitely annulled by the scientific criticism 
of the last few decades. 

The extreme importance of the subject leads us to 
oppose to these untenable " proofs of immortality " a 
brief exposition of the sound scientific arguments 
against it. The physiological argument shows that 
the human soul is not an independent, immaterial 
substance, but, like the soul of all the higher animals, 
merely a collective title for the sum-total of man's cere- 
bral functions ; and these are just as much determined 
by physical and chemical processes as any of the other 
vital functions, and just as amenable to the law of sub- 
stance. The histological argument is based on the ex- 
tremely complicated microscopic structure of the brain ; 
it shows us the true " elementary organs of the soul " 
in the ganglionic cells. The experimental argument 
proves that the various functions of the soul are bound 
up with certain special parts of the brain, and cannot 
be exercised unless these are in a normal condition; 
if the areas are destroyed, their function is extin- 
guished; and this is especially applicable to the "or- 
gans of thought," the four central instruments of men- 
tal activity. The pathological argument is the com- 
plement of the physiological ; when certain parts of the 
brain (the centres of speech, sight, hearing, etc.) are 
destroyed by sickness, their activity (speech, vision, 
hearing, etc.) disappears; in this way nature herself 
makes the decisive physiological experiment. The 
ontogenetic argument puts before us the facts of the 
development of the soul in the individual ; we see how 
the child-soul gradually unfolds its various powers; 
the youth presents them in full bloom, the mature man 
shows their ripe fruit; in old age we see the gradual 
decay of the psychic powers, corresponding to the senile 



degeneration of the brain. The phylogenetic argument 
derives its strength from palaeontology, and the com- 
parative anatomy and physiology of the brain; co- 
operating with and completing each other, these sciences 
prove to the hilt that the human brain (and, conse- 
quently, its function the soul) has been evolved step 
by step from that of the mammal, and, still further 
back, from that of the lower vertebrate. 

These inquiries, which might be supplemented by 
many other results of modern science, prove the old 
dogma of the immortality of the soul to be absolutely 
untenable; in the twentieth century it will not be re- 
garded as a subject of serious scientific research, but 
will be left wholly to transcendental "faith." The 
"critique of pure reason" shows this treasured faith 
to be a mere superstition, like the belief in a personal 
God which generally accompanies it. Yet even to- 
day millions of " believers " not only of the lower, 
uneducated masses, but even of the most cultured 
classes look on this superstition as their dearest pos- 
session and their most "priceless treasure." It is, 
therefore, necessary to enter more deeply into the sub- 
ject, and assuming it to be true to make a critical 
inquiry into its practical value. It soon becomes ap- 
parent to the impartial critic that this value rests, for 
the most part, on fancy, on the want of clear judgment 
and consecutive thought. It is my firm and honest 
conviction that a definitive abandonment of these 
"athanatist illusions" would involve no painful loss, 
but an inestimable positive gain for humanity. 

Man's "emotional craving" clings to the belief on 
immortality for two main reasons : firstly, in the hope 
of better conditions of life beyond the grave ; and, sec- 
ondly, in the hope of seeing once more the dear and 
is 205 


loved ones whom death has torn from us. As for the 
first hope, it corresponds to a natural feeling of the 
justice of compensation, which is quite correct subjec- 
tively, but has no objective validity whatever. We 
make our claim for an indemnity for the unnumbered 
defects and sorrows of our earthly existence, without 
the slightest real prospect or guarantee of receiving it. 
We long for an eternal life in which we shall meet no 
sadness and no pain, but an unbounded peace and joy. 
The pictures that most men form of this blissful exist- 
ence are extremely curious; the immaterial soul is 
placed in the midst of grossly material pleasures. The 
imagination of each believer paints the enduring splen- 
dor according to his personal taste, The American Ind- 
ian, whose athanatism Schiller has so well depicted, 
trusts to find in his Paradise the finest hunting-grounds 
with innumerable hordes of buffaloes and bears; the 
Eskimo looks forward to sun-tipped icebergs with an 
inexhaustible supply of bears, seals, and other polar 
animals; the effeminate Cingalese frames his Para- 
dise on the wonderful island-paradise of Ceylon with 
its noble gardens and forests adding that there will 
be unlimited supplies of rice and curry, of cocoanuts 
and other fruit, always at hand; the Mohammedan 
Arab believes it will be a place of shady gardens of 
flowers, watered by cool springs, and filled with lovely 
maidens; the Catholic fisherman of Sicily looks for- 
ward to a daily superabundance of the most valuable 
fishes and the finest macaroni, and eternal absolution 
for all his sins, which he can go on committing in his 
eternal home; the evangelical of North Europe longs 
for an immense Gothic cathedral, in which he can chant 
the praises of the Lord of Hosts for all eternity. In a 
word, each believer really expects his eternal life to be 



a direct continuation of his individual life on earth, 
only in a " much improved and enlarged edition." 

We must lay special stress on the thoroughly mate- 
rialistic character of Christian athanatism, which is 
closely connected with the absurd dogma of the " resur- 
rection of the body." As thousands of paintings of 
famous masters inform us, the bodies that have risen 
again, with the souls that have been born again, walk 
about in heaven just as they did in this vale of tears ; 
they see God with their eyes, they hear His voice with 
their ears, they sing hymns to His praise with their 
larynx, and so forth. In fine, the modern inhabitants 
of the Christian Paradise have the same dual character 
of body and soul, the same organs of an earthly body, 
as our ancient ancestors had in Odin's Hall in Wal- 
halla, as the "immortal" Turks and Arabs have in 
Mohammed's lovely gardens, as the old Greek demi- 
gods and heroes had in the enjoyment of nectar and 
ambrosia at the table of Zeus. 

But, however gloriously we may depict this eternal 
life in Paradise, it remains endless in duration. Do 
we realize what " eternity " means? the uninterrupted 
continuance of our individual life forever! The pro- 
found legend of the "wandering Jew," the fruitless 
search for rest of the unhappy Ahasuerus, should teach 
us to appreciate such an " eternal life " at its true value. 
The best we can desire after a courageous life, spent in 
doing good according to our light, is the eternal peace 
of the grave. " Lord, give them an eternal rest." 

Any impartial scholar who is acquainted with geo- 
logical calculations of time, and has reflected on the 
long series of millions of years the organic history of 
the earth has occupied, must admit that the crude no- 
tion of an eternal life is not a comfort, but a fearful 



menace, to the best of men. Only want of clear judg- 
ment and consecutive thought can dispute it. 

The best and most plausible ground for athanatism 
is found in the hope that immortality will reunite us 
to the beloved friends who have been prematurely taken 
from us by some grim mischance. But even this sup- 
posed good fortune proves to be an illusion on closer 
inquiry; and in any case it would be greatly marred 
by the prospect of meeting the less agreeable acquaint- 
ances and the enemies who have troubled our existence 
here below. Even the closest family ties would in- 
volve many a difficulty. There are plenty of men who 
would gladly sacrifice all the glories of Paradise if it 
meant the eternal companionship of their " better half * 
and their mother-in-law. It is more than questionable 
whether Henry VIII. would like the prospect of living 
eternally with his six wives; or Augustus the Strong 
of Poland, who had a hundred mistresses and three 
hundred and fifty-two children. As he was on good 
terms with the Vicar of Christ, he must be assumed to 
be in Paradise, in spite of his sins, and in spite of the 
fact that his mad military ventures cost the lives of 
more than a hundred thousand Saxons. 

Another insoluble difficulty faces the athanatist 
when he asks in what stage of their individual develop- 
ment the disembodied souls will spend their eternal 
life. Will the new-born infant develop its psychic 
powers in heaven under the same hard conditions of 
the " struggle for life " which educate man here on 
earth? Will the talented youth who has fallen in the 
wholesale murder of war unfold his rich, unused men- 
tal powers in Walhalla? Will the feeble, childish old 
man, who has filled the world with the fame of his 
deeds in the ripeness of his age, live forever in mental 



decay? Or will he return to an earlier stage of devel- 
opment? If the immortal souls in Olympus are to live 
in a condition of rejuvenescence and perfectness, then 
both the stimulus to the formation of, and the interest 
in, personality disappear for them. 

Not less impossible, in the light of pure reason, do 
we find the anthropistic myth of the " last judgment,* 
and the separation of the souls of men into two great 
groups, of which one is destined for the eternal joys of 
Paradise and the other for the eternal torments of hell 
and that from a personal God who is called the 
* Father of Love " ! And it is this " Universal Father " 
who has himself created the conditions of heredity and 
adaptation, in virtue of which the elect, on the one 
side, were bound to pursue the path towards eternal 
bliss, and the luckless poor and miserable, on the other 
hand, were driven into the paths of the damned? 

A critical comparison of the countless and manifold 
fantasies which belief in immortality has produced 
during the last few thousand years in the different 
races and religions yields a most remarkable picture. 
An intensely interesting presentation of it, based on 
most extensive original research, may be found in 
Adalbert Svoboda's distinguished works, The Illusion 
of the Soul and Forms of Faith. However absurd and 
inconsistent with modern knowledge most of these 
myths seem to be, they still play an important part, 
and, as " postulates of practical reason/' they exercise 
a powerful influence on the opinions of individuals and 
on the destiny of races. 

The idealist and spiritualist philosophy of the day 
will freely grant that these prevalent materialistic 
forms of belief in immortality are untenable; it will 
say that the refined idea of an immaterial soul, a Pla 



tonic " idea " or a transcendental psychic substance, 
must be substituted for them. But modern realism 
can have nothing whatever to do with these incompre- 
hensible notions ; they satisfy neither the mind's feel- 
ing of causality nor the yearning of our emotions. If 
we take a comprehensive glance at all that modern 
anthropology, psychology, and cosmology teach with 
regard to athanatism, we are forced to this definite con- 
clusion : " The belief in the immortality of the human 
soul is a dogma which is in hopeless contradiction with 
the most solid empirical truths of modern science." 


The Fundamental Chemical Law of the Constancy of Matter 
The Fundamental Physical Law of the Conservation of En- 
ergy Combination of Both Laws in the Law of Substance 
The Kinetic, Pyknotic, and Dualistic Ideas of Substance 
Monism of Matter Ponderable Matter Atoms and Elements 
Affinity of the Elements The Soul of the Atom (Feeling 
and Inclination) Existence and Character of Ether Ether 
and Ponderable Matter Force and Energy Potential and 
Actual Force Unity of Natural Forces Supremacy of the 
Law of Substance 

'T'HE supreme and all-pervading law of nature, the 
true and only cosmological law, is, in my opin- 
ion, the law of substance ; its discovery and establish- 
ment is the greatest intellectual triumph of the nine- 
teenth century, in the sense that all other known laws 
of nature are subordinate to it. Under the name of 
" law of substance " we embrace two supreme laws of 
different origin and age the older is the chemical law 
of the " conservation of matter," and the younger is 
the physical law of the "conservation of energy."* It 
will be self-evident to many readers, and it is acknowl- 
edged by most of the scientific men of the day, that 
these two great laws are essentially inseparable. This 
fundamental thesis, however, is still much contested 

* Cf . Monism, by Ernst Haeckel. 


in some quarters, and we must proceed to furnish the 
proof of it. But we must first devote a few words to 
each of the two laws. 

The law of the "persistence" or "indestructibility of 
matter," established by Lavoisier in 1789, may be for- 
mulated thus : The sum of matter, which fills infinite 
space, is unchangeable. A body has merely changed 
its form, when it seems to have disappeared. When 
coal burns, it is changed into carbonic-acid gas by com- 
bination with the oxygen of the atmosphere; when a 
piece of sugar melts in water, it merely passes from 
the solid to the fluid condition. In the same way, it is 
merely a question of change of form in the cases where 
a new body seems to be produced. A shower of rain 
is the moisture of the atmosphere cast down in the form 
of drops of water ; when a piece of iron rusts, the sur- 
face layer of the metal has combined with water and 
with atmospheric oxygen, and formed a " rust," or oxy- 
hydrate of iron. Nowhere in nature do we find an 
example of the production, or " creation," of new 
matter; nowhere does a particle of existing matter 
pass entirely away. This empirical truth is now the 
unquestionable foundation of chemistry; it may be 
directly verified at any moment by means of the bal- 
ance. To the great French chemist Lavoisier belongs 
the high merit of first making this experiment with the 
balance! At the present day the scientist, who is oc- 
cupied from one end of the year to the other with the 
study of natural phenomena, is so firmly convinced of 
the absolute " constancy " of matter that he is no longer 
able to imagine the contrary state of things. 

We may formulate the " law of the persistence of force " 
or "conservation of energy" thus: The sum of force, 
which is at work in infinite space and produces all phe- 



nomena, is unchangeable. When the locomotive rushes 
along the line, the potential energy of the steam is trans- 
formed into the kinetic or actual energy of the mechan- 
ical movement; when we hear its shrill whistle, as it 
speeds along, the sound-waves of the vibrating atmos- 
phere are conveyed through the tympanum and the 
three bones of the ear into the inner labyrinth, and 
thence transferred by the auditory nerve to the acoustic 
ganglionic cells which form the centre of hearing in 
the temporal lobe of the gray bed of the brain. The 
whole marvellous panorama of life that spreads over 
the surface of our globe is, in the last analysis, trans- 
formed sunlight. It is well known how the remark- 
able progress of technical science has made it possible 
for us to convert the different physical forces from one 
form to another; heat may be changed into molar 
movement, or movement of mass; this in turn into 
light or sound, and then into electricity, and so forth. 
Accurate measurement of the quantity of force which 
is used in this metamorphosis has shown that it is " con- 
stant" or unchanged. No particle of living energy is 
ever extinguished; no particle is ever created anew. 
Friedrich Mohr, of Bonn, was very near to the discov- 
ery of this great fact in 1837, but the discovery was 
actually made by the able Swabian physician, Robert 
Mayer, of Heilbronn, in 1842. Independently of Mayer, 
however, the principle was reached almost at the same 
time by the famous physiologist, Hermann Helmholtz ; 
five years afterwards he pointed out its general appli- 
cation to, and fertility in, every branch of physics. We 
ought to say to-day that it rules also in the entire prov- 
ince of physiology that is, of "organic physics"; 
but on that point we meet a strenuous opposition from 
the vitalistic biologists and the dualist and spiritualist 



philosophers. For these the peculiar " spiritual forces " 
of human nature are a group of " free " forces, not sub- 
ject to the law of energy ; the idea is closely connected 
with the dogma of the " freedom of the will." We have, 
however, already seen (p. 204) that the dogma is un- 
tenable. Modern physics draws a distinction between 
" force " and " energy/' but our general observations 
so far have not needed a reference to it. 

The conviction that these two great cosmic theorems, 
the chemical law of the persistence of matter and the 
physical law of the persistence of force, are fundament- 
ally one, is of the utmost importance in our monistic 
system. The two theories are just as intimately united 
as their objects matter and force or energy. Indeed, 
this fundamental unity of the two laws is self-evident 
to many monistic scientists and philosophers, since they 
merely relate to two different aspects of one and the 
same object, the cosmos. But, however natural the 
thought may be, it is still very far from being general- 
ly accepted. It is stoutly contested by the entire dual- 
istic philosophy, vitalistic biology, and parallelistic 
psychology ; even, in fact, by a few (inconsistent) mon- 
ists, who think they find a check to it in " conscious- 
ness," in the higher mental activity of man, or in other 
phenomena of our "free mental life." 

For my part, I am convinced of the profound im- 
portance of the unifying " law of substance," as an 
expression of the inseparable connection in reality 
of two laws which are only separated in conception. 
That they were not originally taken together and their 
unity recognized from the beginning is merely an ac- 
cident of the date of their respective discoveries. The 
earlier and more accessible chemical law of the per- 
sistence of matter was detected by Lavoisier in 1789, 



and, after a general application of the balance, became 
the basis of exact chemistry. On the other hand, the 
more recondite law of the persistence of force was only 
discovered by Mayer in 1842, and only laid down as the 
basis of exact physics by Helmholtz. The unity of the 
two laws still much disputed is expressed by many 
scientists who are convinced of it in the formula : " Law 
of the persistence of matter and force." In order to have 
a briefer and more convenient expression for this fun- 
damental thought, I proposed some time ago to call it 
the "law of substance" or the "fundamental cosmic 
law"; it might also be called the "universal law," or 
the " law of constancy," or the " axiom of the constancy 
of the universe." In the ultimate analysis it is found 
to be a necessary consequence of the principle of caus- 

The first thinker to introduce the purely monistic con- 
ception of substance into science and appreciate its 
profound importance was the great philosopher Ba- 
ruch Spinoza; his chief work appeared shortly after 
his premature death in 1677, just one hundred years 
before Lavoisier gave empirical proof of the constancy 
of matter by means of the chemist's principal instru- 
ment, the balance. In his stately pantheistic system 
the notion of the world (the universe, or the cosmos) 
is identical with the all-pervading notion of God ; it 
is at one and the same time the purest and most rational 
monism and the clearest and most abstract monotheism. 
This universal substance, this " divine nature of the 
world," shows us two different aspects of its being, or 
two fundamental attributes matter (infinitely extended 
substance) and spirit (the all-embracing energy of 

* Cf . Monism, by Ernst Haeckel. 


thought). All the changes which have since come ovei 
the idea of substance are reduced, on a logical analysis, 
to this supreme thought of Spinoza's ; with Goethe I 
take it to be the loftiest, prof oundest, and truest thought 
of all ages. Every single object in the world which 
comes within the sphere of our cognizance, all individ- 
ual forms of existence, are but special transitory forms 
accidents or modes of substance. These modes 
are material things when we regard them under the 
attribute of extension (or "occupation of space "), but 
forces or ideas when we consider them under the at- 
tribute of thought (or " energy "). To this profound 
thought of Spinoza our purified monism returns after 
a lapse of two hundred years ; for us, too, matter (space- 
filling substance) and energy (moving force) are but 
two inseparable attributes of the one underlying sub- 

Among the various modifications which the funda- 
mental idea of substance has undergone in modern 
physics, in association with the prevalent atomism, 
we shall select only two of the most divergent theories 
for a brief discussion, the kinetic and the pyknotic. 
Both theories agree that we have succeeded in reducing 
all the different forces of nature to one common original 
force; gravity and chemical action, electricity and 
magnetism, light and heat, etc., are only different man- 
ifestations, forms, or dynamodes, of a single primitive 
force (prodynamis) . This fundamental force is gen- 
erally conceived as a vibratory motion of the smallest 
particles of matter a vibration of atoms. The atoms 
themselves, according to the usual " kinetic theory of 
substance," are dead, separate particles of matter, which 
dance to and fro in empty space and act at a distance. 
The real founder and most distinguished representative 



of the kinetic theory is Newton, the famous discoverer 
of the law of gravitation. In his great work, the Philo- 
sophiae Naturalis Principia Mathematica (1687), ne 
showed that throughout the universe the same law of 
attraction controls the unvarying constancy of gravi- 
tation; the attraction of two particles being in direct 
proportion to their mass and in inverse proportion to 
the square of their distance. This universal force of 
gravity is at work in the fall of an apple and the tidal 
wave no less than in the course of the planets round 
the sun and the movements of all the heavenly bodies. 
Newton had the immortal merit of establishing the law 
of gravitation and embodying it in an indisputable 
mathematical formula. Yet this dead mathematical 
formula, on which most scientists lay great stress, as 
so frequently happens, gives us merely the quantitative 
demonstration of the theory; it gives us no insight 
whatever into the qualitative nature of the phenomena. 
The action at a distance without a medium, which New- 
ton deduced from his law of gravitation, and which be- 
came one of the most serious and most dangerous dog- 
mas of later physics, does not afford the slightest ex- 
planation of the real causes of attraction; indeed, it 
long obstructed our way to the real discovery of them. 
I cannot but suspect that his speculations on this mys- 
terious action at a distance contributed not a little to 
the leading of the great English mathematician into 
the obscure labyrinth of mystic dreams and theistic 
superstition in which he passed the last thirty-four years 
of his life ; we find him, at the end, giving metaphysical 
hypotheses on the predictions of Daniel and on the 
paradoxical fantasies of St. John. 

In fundamental opposition to the theory of vibra- 
tion, or the kinetic theory of substance, we have the 



modern " theory of condensation," or the pyknotic 
theory of substance. It is most ably established in 
the suggestive work of J. C. Vogt on The Nature of 
Electricity and Magnetism on the Basis of a Simplified 
Conception of Substance (1891). Vogt assumes the 
primitive force of the world, the universal prodynamis, 
to be, not the vibration or oscillation of particles in 
empty space, but the condensation of a simple primitive 
substance, which fills the infinity of space in an un- 
broken continuity. Its sole inherent mechanical form 
of activity consists in a tendency to condensation or 
contraction, which produces infinitesimal centres of 
condensation ; these may change their degree of thick- 
ness, and, therefore, their volume, but are constant as 
such. These minute parts of the universal substance, 
the centres of condensation, which might be called 
pyknatoms, correspond in general to the ultimate sep- 
arate atoms of the kinetic theory; they differ, how- 
ever, very considerably in that they are credited with 
sensation and inclination (or will - movement of the 
simplest form), with souls, in a certain sense in har- 
mony with the old theory of Empedocles of the " love 
and hatred of the elements." Moreover, these " atoms 
with souls" do not float in empty space, but in 
the continuous, extremely attenuated intermediate 
substance, which represents the uncondensed portion 
of the primitive matter. By means of certain "con- 
stellations, centres of perturbation, or systems of de- 
formation/' great masses of centres of condensation 
quickly unite in immense proportions, and so obtain a 
preponderance over the surrounding masses. By that 
process the primitive substance, which in its original 
state of quiescence had the same mean consistency 
throughout, divides or differentiates into two kinds. 



The centres of disturbance, which positively exceed the 
mean consistency in virtue of the pyknosis or conden- 
sation, form the ponderable matter of bodies ; the finer, 
intermediate substance, which occupies the space be- 
tween them, and negatively falls below the mean con- 
sistency, forms the ether, or imponderable matter. As 
a consequence of this division into mass and ether there 
ensues a ceaseless struggle between the two antago- 
nistic elements, and this struggle is the source of all 
physical processes. The positive ponderable matter, 
the element with the feeling of like or desire, is contin- 
ually striving to complete the process of condensation, 
and thus collecting an enormous amount of potential 
energy; the negative, imponderable matter, on the 
other hand, offers a perpetual and equal resistance to 
the further increase of its strain and of the feeling of 
dislike connected therewith, and thus gathers the ut- 
most amount of actual ene:^y. 

We cannot go any further here into the details of the 
brilliant theory of J. C. Vogt. The interested reader 
cannot do better than have recourse to the second vol- 
ume of the above work for a clear, popular exposition 
of the difficult problem. I am myself too little informed 
in physics and mathematics to enter into a critical dis- 
cussion of its lights and shades ; still, I think that this 
pyknotic theory of substance will prove more accept- 
able to every biologist who is convinced of the unity 
of nature than the kinetic theory which prevails in 
physics to-day. A misunderstanding may easily arise 
from the fact that Vogt puts his process of condensa- 
tion in explicit contradiction with the general phenom- 
enon of motion ; but it must be remembered that he is 
speaking of vibratory movement in the sense of the 
physicist. His hypothetical " condensation " is just as 



much determined by a movement of substance as is the 
hypothetical "vibration"; only the kind of movement 
and the relation of the moving elements are very dif- 
ferent in the two hypotheses. Moreover, it is not the 
whole theory of vibration, but only an important section 
of it, that is contradicted by the theory of condensation. 
Modern physics, for the most part, still firmly ad- 
heres to the older theory of vibration, to the idea of an 
actio in distans and the eternal vibration of dead atoms 
in empty space; it rejects the pyknotic theory. Al- 
though Vogt's theory may be still far from perfect, 
and his original speculations may be marred by many 
errors, yet I think he has rendered a very good service 
in eliminating the untenable principles of the kinetic 
theory of substance. As to my own opinion and that 
of many other scientists I must lay down the following 
theses, which are involved in Vogt's pyknotic theory, 
as indispensable for a truly monistic view of substance, 
and one that covers the whole field of organic and in- 
organic nature : 

I. The two fundamental forms of substance, pon- 
derable matter and ether, are not dead and only moved 
by extrinsic force, but they are endowed with sensation 
and will (though, naturally, of the lowest grade) ; they 
experience an inclination for condensation, a dislike of 
strain; they strive after the one and struggle against 
the other. 

II. There is no such thing as empty space; that 
part of space which is not occupied with ponderable 
atoms is filled with ether. 

III. There is no such thing as an action at a dis- 
tance through perfectly empty space; all action of 
bodies upon each other is either determined by imme- 
diate contact or is effected by the mediation of ether. 



Both the theories of substance which we have just 
contrasted are monistic in principle, since the opposi- 
tion between the two conditions of substance mass 
and ether is not original; moreover, they involve a 
continuous immediate contact and reciprocal action of 
the two elements. It is otherwise with the dualistic 
theories of substance which still obtain in the idealist 
and spiritualist philosophy, and which have the sup- 
port of a powerful theology, in so far as theology in- 
dulges in such metaphysical speculations. These 
theories draw a distinction between two entirely dif- 
ferent kinds of substance, material and immaterial. 
Material substance enters into the composition of the 
bodies which are the object of physics and chemistry ; 
the law of the persistence of matter and force is con- 
fined to this world (apart from a belief in its " creation 
from nothing" and other miracles). Immaterial sub- 
stance is found in the " spiritual world " to which the 
law does not extend; in this province the laws of 
physics and chemistry are either entirely inapplicable 
or they are subordinated to a " vital force," or a " free 
will," or a " divine omnipotence," or some other phan- 
tom which is beyond the ken of critical science. In 
truth, these profound errors need no further refutation 
to-day, for experience has never yet discovered for us 
a single immaterial substance, a single force which is 
not dependent on matter, or a single form of energy 
which is not exerted by material movement, whether it 
be of mass, or of ether, or of both. Even the most elabo- 
rate and most perfect forms of energy that we know the 
psychic life of the higher animals, the thought and rea- 
son of man depend on material processes, or changes in 
the neuroplasm of the ganglionic cells ; they are incon- 
ceivable apart from such modifications. I have already 

16 221 


shown (chap, xi.) that the physiological hypothesis of a 
special, immaterial " soul-substance " is untenable. 

The study of ponderable matter is primarily the con- 
cern of chemistry. Few are ignorant of the astonish- 
ing theoretical progress which this science has made 
in the course of the century and the immense practical 
influence it has had on every aspect of modern life. 
We shall confine ourselves here to a few remarks on 
the more important questions which concern the nat- 
ure of ponderable matter. It is well known that an- 
alytical chemistry has succeeded in resolving the im- 
mense variety of bodies in nature into a small number 
of simple elements that is, simple bodies which are 
incapable of further analysis. The number of these 
elements is about seventy. Only fourteen of them are 
widely distributed on the earth and of much practi- 
cal importance; the majority are rare elements (prin- 
cipally metals) of little practical moment. The af- 
finity of these groups of elements, and the remark- 
able proportions of their atomic weights, which 
Lothar Meyer and Mendelejeff have proved in their 
Periodic System of the Elements, make it extremely 
probable that they are not absolute species of ponder- 
able matter that is, not eternally unchangeable par- 
ticles. The seventy elements have in that system 
been distributed into eight leading groups, and ar- 
ranged in them according to their atomic weight, so 
that the elements which have a chemical affinity are 
formed into families. The relations of the various 
groups in such a natural system of the elements recall, 
on the one hand, similar relations of the innumerable 
compounds of carbon, and, again, the relations of par- 
allel groups in the natural arrangement of the animal 
and plant species. Since in the latter cases the "af- 



finity " of the related forms is based on descent from a 
common parent form, it seems very probable that the 
same holds good of the families and orders of the chem- 
ical elements. We may, therefore, conclude that the 
" empirical elements " we now know are not really sim- 
ple, ultimate, and unchangeable forms of matter, but 
compounds of homogeneous, simple, primitive atoms, 
variously distributed as to number and grouping. The 
recent speculations of Gustav Wendt, Wilhelm Preyer, 
Sir W. Crookes, and others, have pointed out how we 
may conceive the evolution of the elements from a sim- 
ple primitive material, the prothyl. 

The modern atomistic theory, which is regarded as 
an indispensable instrument in chemistry to-day, must 
be carefully distinguished from the old philosophic 
atomism which was taught more than two thousand 
years ago by a group of distinguished thinkers of 
antiquity Leucippus, Democritus, and Epicurus: it 
was considerably developed and modified later on by 
Descartes, Hobbes, Leibnitz, and other famous philos- 
ophers. But it was not until 1808 that modern atomism 
assumed a definite and acceptable form, and was fur- 
nished with an empirical basis by Dalton, who formu- 
lated the "law of simple and multiple proportions" 
in the formation of chemical combinations. He first 
determined the atomic weight of the different elements, 
and thus created the solid and exact foundation on 
which more recent chemical theories are based; these 
are all atomistic, in the sense that they assume the 
elements to be made up of homogeneous, infinitesimal, 
distinct particles, which are incapable of further an- 
alysis. That does not touch the question of the real 
nature of the atoms their form, size, psychology, etc. 
These atomic qualities are merely hypothetical ; while 



the chemistry of the atoms, their " chemical affinity"" 
that is, the constant proportion in which they com- 
bine with the atoms of other elements is empirical.* 
The different relation of the various elements towards 
each other, which chemistry calls " affinity/' is one of 
the most important properties of ponderable matter; 
it is manifested in the different relative quantities or 
proportions of their combination in the intensity of 
its consummation. Every shade of inclination, from 
complete indifference to the fiercest passion, is exem- 
plified in the chemical relation of the various elements 
towards each other, just as we find in the psychology 
of man, and especially in the life of the sexes. Goethe, 
in his classical romance, Affinities, compared the re- 
lations of pairs of lovers with the phenomenon of the 
same name in the formation of chemical combinations. 
The irresistible passion that draws Edward to the sym- 
pathetic Ottilia, or Paris to Helen, and leaps over all 
bounds of reason and morality, is the same powerful 
" unconscious " attractive force which impels the living 
spermatozoon to force an entrance into the ovum in 
the fertilization of the egg of the animal or plant the 
same impetuous movement which unites two atoms of 
hydrogen to one atom of oxygen for the formation of a 
molecule of water. This fundamental unity of affinity 
in the whole of nature, from the simplest chemical process 
to the most complicated love story, was recognized by 
the great Greek scientist, Empedocles, in the fifth cen- 
tury B.C., in his theory of "the love and hatred of the 
elements." It receives empirical confirmation from 
the interesting progress of cellular psychology, the 
great significance of which we have only learned to 

* Cf. Monism' by Ernst Haeckel. 


appreciate in the last thirty years. On those phenom- 
ena we base our conviction that even the atom is not 
without a rudimentary form of sensation and will, or. 
as it is better expressed, of feeling (aesthesis) and in- 
clination (tropesis) that is, a universal " soul " of 
the simplest character. The same must be said of the 
molecules which are composed of two or more atoms. 
Further combinations of different kinds of these mole- 
cules give rise to simple and, subsequently, complex 
chemical compounds, in the activity of which the same 
phenomena are repeated in a more complicated form. 

The study of ether, or imponderable matter, per- 
tains principally to physics. The existence of an ex- 
tremely attenuated medium, filling the whole of space 
outside of ponderable matter, was known and applied 
to the elucidation of various phenomena (especially 
light) a long time ago ; but it was not until the second 
half of the nineteenth century that we became more 
closely acquainted with this remarkable substance, in 
connection with our astonishing empirical discoveries in 
the province of electricity, with their experimental de- 
tection, their theoretical interpretation, and their prac- 
tical application. The path was opened in particular 
by the famous researches of Heinrich Hertz, of Bonn, 
in 1888. The premature death of a brilliant young 
physicist of so much promise cannot be sufficiently 
deplored. Like the premature death of Spinoza, Ra- 
phael, Schubert, and many other great men, it is one 
of those brutal facts of human history which are enough 
of themselves to destroy the untenable myth of a " wise 
Providence" and an "All-loving Father in heaven." 

The existence of ether (or cosmic ether) as a real ele- 
ment is a positive fact, and has been known as such 
for the last twelve years. We sometimes read even 



to-day that ether is a "pure hypothesis"; this erro- 
neous assertion comes not only from uninformed phi- 
losophers and "popular" writers, but even from cer- 
tain " prudent and exact physicists." But there would 
be just as much reason to deny the existence of pon- 
derable matter. As a matter of fact, there are meta- 
physicians who accomplish even this feat, and whose 
highest wisdom lies in denying or calling into ques- 
tion the existence of an external universe; accord- 
ing to them only one real entity exists their own 
precious personality, or, to be more correct, their im- 
mortal soul. Several modern physiologists have em- 
braced this ultra -idealist view, which is to be found 
in Descartes, Berkeley, Fichte, and others. Their 
" psycho - monism " affirms : " One thing only exists, 
and that is my own mind." This audacious spiritual- 
ism seems to us to rest on an erroneous inference from 
Kant's correct critical theory, that we can know the 
outer world only in the phenomenal aspect which is 
accessible to our human organs of thought the brain 
and the organs of sense. If by those means we can 
attain only an imperfect and limited knowledge of the 
material world, that is no reason for denying its exist- 
ence altogether. In my opinion, the existence of ether 
is as certain as that of ponderable matter as certain 
as my own existence, as I reflect and write on it. As 
we assure ourselves of the existence of ponderable mat- 
ter by its mass and weight, by chemical and mechani- 
cal experiments, so we prove that of ether by the expe- 
riences and experiments of optics and electricity. 

Although, however, the existence of ether is now 
regarded as a positive fact by nearly all physicists, 
and although many effects of this remarkable sub- 
stance are familiar to us through an extensive experi- 



ence, especially in the way of optical and electrical 
experiments, yet we are still far from being clear and 
confident as to its real character. The views of the 
most eminent physicists, who have made a special 
study of it, are extremely divergent; they frequently 
contradict each other on the most important points. 
One is, therefore, free to choose among the contradic- 
tory hypotheses according to one's knowledge and 
judgment. I will put in the following eight theses 
the view which has approved itself to me after mature 
reflection on the subject, though I am no expert in 
this department : 

I. Ether fills the whole of space, in so far as it is 
not occupied by ponderable matter, as a continuous 
substance ; it fully occupies the space between the 
atoms of ponderable matter. 

II. Ether has probably no chemical quality, and 
is not composed of atoms. If it be supposed that it 
consists of minute homogeneous atoms (for instance, 
indivisible etheric particles of a uniform size), it must 
be further supposed that there is something else be- 
tween these atoms, either "empty space" or a third, 
completely unknown medium, a purely hypothetical 
" interether " ; the question as to the nature of this 
brings us back to the original difficulty, and so on in 

III. As the idea of an empty space and an action 
at a distance is scarcely possible in the present condi- 
tion of our knowledge (at least it does not help to a 
clear monistic view), I postulate for ether a special 
structure which is not atomistic, like that of ponderable 
matter, and which may provisionally be called (with- 
out further determination) etheric or dynamic structure. 

IV. The consistency of ether is also peculiar, on 



our rrypothesis, and different from that of ponderable 
matter. It is neither gaseous, as some conceive, nor 
solid, as others suppose; the best idea of it can be 
formed by comparison with an extremely attenuated, 
elastic, and light jelly. 

V. Ether may be called imponderable matter in the 
sense that we have no means of determining its weight 
experimentally. If it really has weight, as is very 
probable, it must be so slight as to be far below the 
capacity of our most delicate balance. Some physi- 
cists have attempted to determine its weight by the 
energy of the light-waves, and have discovered that it 
is some fifteen trillion times lighter than atmospheric 
air ; on that hypothesis a sphere of ether of the size of 
our earth would weigh at least two hundred and fifty 
pounds (?). 

VI. The etheric consistency may probably (in ac- 
cordance with the pyknotic theory) pass into the gas- 
eous state under certain conditions by progressive con- 
densation, just as a gas may be converted into a fluid, 
and ultimately into a solid, by lowering its tempera- 

VII. Consequently, these three conditions of mat- 
ter may be arranged (and it is a point of great impor- 
tance in our monistic cosmogony) in a genetic, contin- 
uous order. We may distinguish five stages in it : (i) 
the etheric, (2) the gaseous, (3) the fluid, (4) the vis- 
cous (in the living protoplasm), and (5) the solid state. 

VIII Ether is boundless and immeasurable, like 
the space it occupies. It is in eternal motion; and 
this specific movement of ether (it is immaterial whether 
we conceive it as vibration, strain, condensation, etc.), 
in reciprocal action with mass-movement (or gravita- 
tion), is the ultimate cause of all phenomena. 



" The great question of the nature of ether," as 
Hertz justly calls it, includes the question of its re- 
lation to ponderable matter; for these two forms of 
matter are not only always in the closest external con- 
tact, but also in eternal, dynamic, reciprocal action. 
We may divide the most general phenomena of nature, 
which are distinguished by physics as natural forces 
or " functions of matter/' into two groups ; the first of 
them may be regarded mainly (though not exclusively) 
as a function of ether, and the second a function of 
ponderable matter as in the following scheme which 
I take from my Monism : 


ETHER Imponderable. 

MASS Ponderable. 

I. Consistency! 

Etheric (i.e., neither gaseous, 
nor fluid nor solid). 
2. Structure: 

Not atomistic, not made up of 
separate particles (atoms), but 

3. Chief Functions': 
Light, radiant heat, electricity, 
and magnetism. 

i. Consistency': 

Not etheric (but gaseous, fluid, 
or solid). 

2. Structure! 

Atomistic, made up of infinitesi- 
mal, distinct particles (atoms) 

3. Chief Functions! 
Gravity, inertia, molecular heat, 
and chemical affinity. 

The two groups of functions of matter, which we have 
opposed in this table, may, to some extent, be regarded 
as the outcome of the first " division of labor" in the 
development of matter, the "primary ergonomy of 
matter." But this distinction must not be supposed 
to involve an absolute separation of the two antithetic 
groups; they always retain their connection, and are 



in constant reciprocal action. It is well known that 
the optical and electrical phenomena of ether are close- 
ly connected with mechanical and chemical changes 
in ponderable elements; the radiant heat of ether may 
be directly converted into the mechanical heat of the 
mass ; gravitation is impossible unless the ether effects 
the mutual attraction of the separated atoms, because 
we cannot admit the idea of an actio in distans. In 
like manner, the conversion of one form of energy into 
another, as indicated in the law of the persistence of 
force, illustrates the constant reciprocity of the two 
chief types of substance, ether and mass. 

The great law of nature, which, under the title of the 
" law of substance," we put at the head of all physical 
considerations, was conceived as the law of " the persist- 
ence of force " by Robert Meyer, who first formulated it, 
and Helmholtz, who continued the work. Another Ger- 
man scientist, Friedrich Mohr, of Bonn, had clearly 
outlined it in its main features ten years earlier (1837). 
The old idea of force was, after a time, differentiated 
by modern physics from that of energy, which was at 
first synonymous with it. Hence the law is now usu- 
ally called the " law of the persistence of energy. " How- 
ever this finer distinction need not enter into the gen- 
eral consideration, to which I must confine myself here, 
and into the question of the great principle of the " per- 
sistence of substance." The interested reader will find 
a very clear treatment of the question in Tyndall's ex- 
cellent paper on " The Fundamental Law of Nature," 
in his Fragments of Science. It fully explains the 
broad significance of this profound cosmic law, and 
points out its application to the main problems of very 
different branches of science. We shall confine our 
attention to the important fact that the " principle of 



energy " and the correlative idea of the unity of natu* 
ral forces, on the basis of a common origin, are now 
accepted by all competent physicists, and are re- 
garded as the greatest advance of physics in the nine- 
teenth century. We now know that heat, sound, light, 
chemical action, electricity, and magnetism are all 
modes of motion. We can, by a certain apparatus, 
convert any one of these forces into another, and prove 
by an accurate measurement that not a single particle 
of energy is lost in the process. 

The sum-total of force or energy in the universe re- 
mains constant, no matter what changes take place 
around us; it is eternal and infinite, like the matter 
on which it is inseparably dependent. The whole 
drama of nature apparently consists in an alternation 
of movement and repose; yet the bodies at rest have 
an inalienable quantity of force, just as truly as those 
that are in motion. It is in this movement that the 
potential energy of the former is converted into the 
kinetic energy of the latter. "As the principle of the 
persistence of force takes into account repulsion as 
well as attraction, it affirms that the mechanical value 
of the potential energy and the kinetic energy in the 
material world is a constant quantity. To put it brief- 
ly, the force of the universe is divided into two parts, 
which may be mutually converted, according to a fixed 
relation of value. The diminution of the one involves 
the increase of the other ; the total value remains un- 
changed in the universe." The potential energy and 
the actual, or kinetic, energy are being continually 
transformed from one condition to the other; but the 
infinite sum of force in the world at large never suffers 
the slightest curtailment. 

Once modern physics had established the law of sub- 


stance as far as the simpler relations of inorganic bod- 
ies are concerned, physiology took up the story, and 
proved its application to the entire province of the or- 
ganic world. It showed that all the vital activities 
of the organism without exception are based on a 
constant " reciprocity of force " and a correlative change 
of material, or metabolism, just as much as the simplest 
processes in " lifeless " bodies. Not only the growth 
and the nutrition of plants and animals, but even their 
functions of sensation and movement, their sense-action 
and psychic life, depend on the conversion of potential 
into kinetic energy, and vice versa. This supreme 
law dominates also those elaborate performances of 
the nervous system which we call, in the higher ani- 
mals and man, "the action of the mind." 

Our monistic view, that the great cosmic law applies 
throughout the whole of nature, is of the highest mo- 
ment. For it not only involves, on its positive side, 
the essential unity of the cosmos and the causal con- 
nection of all phenomena that come within our cogni- 
zance, but it also, in a negative way, marks the highest 
intellectual progress, in that it definitely rules out the 
three central dogmas of metaphysics God, freedom, 
and immortality. In assigning mechanical causes to 
phenomena everywhere, the law of substance conies 
into line with the universal law of causality. 


The Notion of Creation Miracles Creation of the Whole Uni- 
verse and of its Various Parts Creation of Substance (Cos- 
mological Creation) Deism : One Creative Day Creation of 
Separate Entities Five Forms of Ontological Creationism 
Theory of Evolution I. Monistic Cosmogony Beginning 
and End of the World The Infinity and Eternity of the Uni- 
verse Space and Time Universum perpetuum mobile En- 
tropy of the Universe II. Monistic Geogeny History of the 
Inorganic and Organic Worlds III. Monistic Biogeny 
Transformism and the Theory of Descent: Lamarck and 
Darwin IV. Monistic Anthropogeny Origin of Man 

'""THE greatest, vastest, and most difficult of all cos- 
mic problems is that of the origin and develop- 
ment of the world the "question of creation," in a 
word. Even to the solution of this most difficult world- 
riddle the nineteenth century has contributed more than 
all its predecessors ; in a certain sense, indeed, it has 
found the solution. We have at least attained to a 
clear view of the fact that all the partial questions of 
creation are indivisibly connected, that they represent 
one single, comprehensive " cosmic problem," and that 
the key to this problem is found in the one magic 
word evolution. The great questions of the crea- 
tion of man, the creation of the animals and plants, 
the creation of the earth and the sun, etc., are all 
parts of the general question, What is the origin of the 



whole world? Has it been created by supernatural 
power, or has it been evolved by a natural process ? What 
are the causes and the manner of this evolution? If 
we succeed in finding the correct answer to one of these 
questions, we have, according to our monistic concep- 
tion of the world, cast a brilliant light on the solution 
of them all, and on the entire cosmic problem. 

The current opinion as to the origin of the world in 
earlier ages was almost a universal belief in creation. 
This belief has been expressed in thousands of inter- 
esting, more or less fabulous, legends, poems, cosmog- 
onies, and myths. A few great philosophers were de- 
void of it, especially those remarkable free-thinkers of 
classical antiquity who first conceived the idea of nat- 
ural evolution. All the creation-myths, on the con- 
trary, were of a supernatural, miraculous, and trans- 
cendental character. Incompetent, as it was, to inves- 
tigate for itself the nature of the world and its origin 
by natural causes, the undeveloped mind naturally 
had recourse to the idea of miracle. In most of these 
creation-myths anthropism was blended with the belief 
in the miraculous. The creator was supposed to have 
constructed the world on a definite plan, just as man 
accomplishes his artificial constructions; the concep- 
tion of the creator was generally completely anthropo- 
morphic, a palpable " anthropistic creationism." The 
" all-mighty maker of heaven and earth," as he is called 
in Genesis and the Catechism, is just as humanly con- 
ceived as the modern creator of Agassiz and Reinke, 
or the intelligent "engineer" of other recent biologists. 

Entering more fully into the notion of creation, we 
can distinguish as two entirely different acts the prq- 
duction of the universe as a whole and the partial pro- 
duction of its various parts, in harmony with Spinoza's 



idea of substance (the universe) and accidents (or modes, 
the individual phenomena of substance). This dis- 
tinction is of great importance, because there are many 
eminent philosophers who admit the one and reject the 

According to this creationist theory, then, God has 
"made the world out of nothing." It is supposed 
that God (a rational, but immaterial, being) existed 1 
by himself for an eternity before he resolved to create 
the world. Some supporters of the theory restrict God's 
creative function to one single act; they believe that 
this extramundane God (the rest of whose life is shroud- 
ed in mystery) created the substance of the world in a 
single moment, endowed it with the faculty of the most 
extensive evolution, and troubled no further about it. 
This view may be found, for instance, in the English 
Deists in many forms. It approaches very close to our 
monistic theory of evolution, only abandoning it in the 
one instant in which God accomplished the creation. 
Other creationists contend that God did not confine 
himself to the mere creation of matter, but that he 
continues to be operative as the " sustainer and ruler 
of the world." Different modifications of this belief 
are found, some approaching very close to pantheism 
and others to complete theism. All these and similar 
forms of belief in creation are incompatible with the 
law of the persistence of matter and force; that law 
knows nothing of a beginning. 

It is interesting to note that E. du Bois-Reymond has 
identified himself with this cosmological creationism 
in his latest speech (on " Neo vitalism," 1894). " It is 
more consonant with the divine omnipotence," he says, 
" to assume that it created the whole material of the 
world in one creative act unthinkable ages ago in such 



wise that it should be endowed with inviolable laws to 
control the origin and the progress of living things 
that, for instance, here on earth rudimentary organ- 
isms should arise from which, without further assist- 
ance, the whole of living nature could be evolved, from 
a primitive bacillus to the graceful palm-wood, from a 
primitive micrococcus to Solomon's lovely wives or to 
the brain of Newton. Thus we are content with one 
creative day, and we derive organic nature mechanic- 
ally, without the aid of either old or new vitalism." 
Du Bois - Reymond here shows, as in the question of 
consciousness, the shallow and illogical character of 
his monistic thought. 

According to another still prevalent theory, which 
may be called "ontological creationism," God not only 
created the world at large, but also its separate contents. 
In the Christian world the old Semitic legend of crea- 
tion, taken from Genesis, is still very widely accepted ; 
even among modern scientists it finds an adherent 
here and there. I have fully entered into the criticism 
of it in the first chapter of my Natural History of Crea- 
tion. The following theories may be enumerated as 
the most interesting modifications of this ontological 
creationism : 

I. Dwtiistic creation. God restricted his interference 
to two creative acts. First he created the inorganic 
world, mere dead substance, to which alone the law of 
energy applies, working blindly and aimlessly in the 
mechanism of material things and the building of the 
mountains; then God attained intelligence and com- 
municated it to the purposive intelligent forces which 
initiate and control organic evolution." 

* Reinke, Die Welt als That (1899). 


II. Trialistic creation. God made the world in three 
creative acts : (a) the creation of the heavens the ex- 
tra-terrestrial world, (b) the creation of the earth (as 
the centre of the world) and of its living inhabitants, 
and (c) the creation of man (in the image and likeness 
of God). This dogma is still widely prevalent among 
theologians and other * educated " people ; it is taught 
as the truth in many of our schools. \ 

III. Heptameral creation ; a creation in seven days 
(teste Moses). Although few educated people really 
believe in this Mosaic myth now, it is still firmly im- 
pressed on our children in the biblical lessons of their 
earliest years. The numerous attempts that have been 
made, especially in England, to harmonize it with the 
modern theory of evolution have entirely failed. It 
obtained some importance in science when Linn6 adopt- 
ed it in the establishment of his system, and based his 
definition of organic species (which he considered to be 
unchangeable) on it : " There are as many different 
species of animals and plants as there were different 
forms created in the beginning by the Infinite." This 
dogma was pretty generally held until the time of 
Darwin (1859), although Lamarck had already proved 
its untenability in 1809. 

IV. Periodic creation. At the beginning of each 
period of the earth's history the whole population of 
animals and plants was created anew, and destroyed 
by a general catastrophe at its close; there were as 
many general creative acts as there are distinct geolog- 
ical periods (the catastrophic theory of Cuvier [1818] 
and Louis Agassiz [1858]). Palaeontology, which 
seemed to support this theory in its more imperfect 
stage, has since completely refuted it. 

V. Individual creation. Every single man and 
17 237 


every individual animal and plant does not arise by 
a natural process of growth, but is created by the favor 
of God. This view of creation is still often met with 
in journals, especially in the " births" column. The 
special talents and features of our children are often 
gratefully acknowledged to be "gifts of God"; their 
hereditary defects fit into another theory. 

The error of these creation-legends and the cognate 
belief in miracles must have been apparent to thought- 
ful minds at an early period ; more than two thousand 
years ago we find that many attempts were made to 
replace them by a rational theory, and to explain the 
origin of the world by natural causes. In the front 
rank, once more, we must place the leaders of the Ionic 
school, with Democritus, Heraclitus, Empedocles, Aris- 
totle, Lucretius, and other ancient philosophers. The 
first imperfect attempts which they made astonish 
us, in a measure, by the flashes of mental light in 
which they anticipate modern ideas. It must be re- 
membered that classical antiquity had not that solid 
groundwork for scientific speculation which has been 
provided by the countless observations and experiments 
of modern scientists. During the Middle Ages es- 
pecially during the domination of the papacy scien- 
tific work in this direction entirely ceased. The tort- 
ure and the stake of the Inquisition insured that an 
unconditional belief in the Hebrew mythology should 
be the final answer to all the questions of creation. 
Even the phenomena which led directly to the observa- 
tion of the facts of evolution the embryology of the 
plant and the animal, and of man remained un- 
noticed, or only excited the interest of an occasional 
keen observer; but their discoveries were ignored or 
forgotten. Moreover, the path to a correct knowledge 



of natural development was barred by the dominant 
theory of preformation, the dogma which held that the 
characteristic form and structure of each animal and 
plant were already sketched in miniature in the germ 
(cf. p. 54). 

The science which we now call the science of evolu- 
tion (in the broadest sense) is, both in its general out- 
line and in its separate parts, a child of the nineteenth 
century; it is one of its most momentous and most 
brilliant achievements. Almost unknown in the pre- 
ceding century, this theory has now become the sure 
foundation of our whole world-system. I have treated 
it exhaustively in my General Morphology (1866), more 
popularly in my Natural History of Creation (1868), 
and in its special application to man in my Anthro- 
pogeny (1874). Here I shall restrict myself to a brief 
survey of the chief advances which the science has made 
in the course of the century. It falls into four sections, 
according to the nature of its object; that is, it deals 
with the natural origin of (i) the cosmos, (2) the earth, 
(3) terrestrial forms of life, and (4) man. 


The first attempt to explain the constitution and the 
mechanical origin of the world in a simple manner by 
"Newtonian laws" that is, by mathematical and 
physical laws was made by Immanuel Kant in the 
famous work of his youth (1755), General History of 
the Earth and Theory of the Heavens. Unfortunately, 
this distinguished and daring work remained almost 
unknown for ninety years ; it was only disinterred in 
1845 by Alexander Humboldt in the first volume of 
his Cosmos. In the mean time the great French math- 



ematician, Pierre Laplace, had arrived independently 
at similar views to those of Kant, and he gave them 
a mathematical foundation in his Exposition du Sys- 
tfrme du Monde (1796). His chief work, the Mecanique 
Celeste, appeared a hundred years ago. The analo- 
gous features of the cosmogony of Kant and Laplace 
consist, as is well known, in a mechanical explana- 
tion of the movements of the planets, and the conclu- 
sion which is drawn therefrom, that all the cosmic 
bodies were formed originally by a condensation of 
rotating nebulous spheres. This tt nebular hypothe- 
sis " has been much improved and supplemented since, 
but it is still the best of all the attempts to explain the 
origin of the world on monistic and mechanical lines. 
It has recently been strongly confirmed and enlarged 
by the theory that this cosmogonic process did not 
simply take place once, but is periodically repeated. 
While new cosmic bodies arise and develop out of ro- 
tating masses of nebula in some parts of the universe, 
in other parts old, extinct, frigid suns come into colli- 
sion, and are once more reduced by the heat generated 
to the condition of nebulae. 

Nearly all the older and the more recent cosmogo- 
nies, including most of those which were inspired by 
Kant and Laplace, started from the popular idea that 
the world had had a beginning. Hence, according to a 
widespread version of the nebular hypothesis, "in the 
beginning" was made a vast nebula of infinitely at- 
tenuated and light material, and at a certain moment 
(" countless ages ago") a movement of rotation was 
imparted to this mass. Given this " first beginning" 
of the cosmogonic movement, it is easy, on mechanical 
principles, to deduce and mathematically establish the 
further phenomena of the formation of the cosmic 



bodies, the separation of the planets, and so forth. 
This first "origin of movement "is Du Bois-Reymond's 
second "world-enigma"; he regards it as transcen- 
dental. Many other scientists and philosophers are 
equally helpless before this difficulty; they resign 
themselves to the notion that we have here a primary 
" supernatural impetus " to the scheme of things, a 
" miracle/' 

In our opinion, this second " world - enigma " is 
solved by the recognition that movement is as innate 
and original a property of substance as is sensation. 
The proof of this monistic assumption is found, first, 
in the law of substance, and, secondly, in the discov- 
eries which astronomy and physics have made in the 
latter half of the century By the spectral analysis of 
Bunsen and Kirchhoff (1860) we have found, not only 
that the millions of bodies, which fill the infinity of 
space, are of the same material as our own sun and 
earth, but also that they are in various stages of evo- 
lution; we have obtained by its aid information as to 
the movements and distances of the stars, which the 
telescope would never have given us. Moreover, the 
telescope itself has been vastly improved, and has, in 
alliance with photography, made a host of scientific 
discoveries of which no one dreamed at the beginning 
of the century. In particular, a closer acquaintance 
with comets, meteorites, star-clusters, and nebulae has 
helped us to realize the great significance of the smaller 
bodies which are found in millions in the space between 
the stars. 

We now know that the paths of the millions of heav- 
enly bodies are changeable, and to some extent irregu- 
lar, whereas the planetary system was formerly thought 
to be constant, and the rotating spheres were described 



as pursuing their orbits in eternal regularity. Astro- 
physics owes much of its triumph to the immense prog- 
ress of other branches of physics, of optics, and elec- 
tricity, and especially of the theory of ether. And here, 
again, our supreme law of substance is found to be one 
of the most valuable achievements of modern science. 
We now know that it rules unconditionally in the most 
distant reaches of space, just as it does in our planetary 
system, in the most minute particle of the earth as 
well as in the smallest cell of our human frame. We 
are, moreover, justified in concluding, if we are not 
logically compelled to conclude, that the persistence 
of matter and force has held good throughout all time 
as it does to-day. Through all eternity the infinite 
universe has been, and is, subject to the law of sub- 

From this great progress of astronomy and physics, 
which mutually elucidate and supplement each other, 
we draw a series of most important conclusions with 
regard to the constitution and evolution of the cosmos, 
and the persistence and transformation of substance. 
Let us put them briefly in the following theses : 

I. The extent of the universe is infinite and un- 
bounded ; it is empty in no part, but everywhere filled 
with substance. 

II. The duration of the world is equally infinite 
and unbounded ; it has no beginning and no end : it 
is eternity. 

III. Substance is everywhere and always in unin- 
terrupted movement and transformation: nowhere is 
there perfect repose and rigidity ; yet the infinite quan- 
tity of matter and of eternally changing force remains 

IV. This universal movement of substance in space 



takes the form of an eternal cycle or of a periodical pro- 
cess of evolution. 

V. The phases of this evolution consist in a peri- 
odic change of consistency, of which the first outcome 
is the primary division into mass and ether the er- 
gonomy of ponderable and imponderable matter. 

VI. This division is effected by a progressive con- 
densation of matter as the formation of countless in- 
finitesimal " centres of condensation/' in which the in- 
herent primitive properties of substance feeling and 
inclination are the active causes. 

VII. While minute and then larger bodies are being 
formed by this pyknotic process in one part of space, 
and the intermediate ether increases its strain, the op- 
posite process the destruction of cosmic bodies by 
collision is taking place in another quarter. 

VIII. The immense quantity of heat which is gen- 
erated in this mechanical process of the collision of 
swiftly moving bodies represents the new kinetic en- 
ergy which effects the movement of the resultant nebu- 
lae and the construction of new rotating bodies. The 
eternal drama begins afresh. Even our mother earth, 
which was formed of part of the gyrating solar system 
millions of ages ago, will grow cold and lifeless after 
the lapse of further millions, and, gradually narrow- 
ing its orbit, will fall eventually into the sun. 

It seems to me that these modern discoveries as to 
the periodic decay and re-birth of cosmic bodies, which 
we owe to the most recent advance of physics and as- 
tronomy, associated with the law of substance, are 
especially important in giving us a clear insight into 
the universal cosmic process of evolution. In their 
light our earth shrinks into the slender proportions 
of a "mote in the sunbeam," of which unnumbered 



millions chase each other through the vast depths of 
space. Our own " human nature/' which exalted itself 
into an image of God in its anthropistic illusion, sinks 
to the level of a placental mammal, which has no more 
value for the universe at large than the ant, the fly of 
a summer's day, the microscopic infusorium, or the 
smallest bacillus. Humanity is but a transitory phase 
of the evolution of an eternal substance, a particular 
phenomenal form of matter and energy, the true pro- 
portion of which we soon perceive when we set it on 
the background of infinite space and eternal time. 

Since Kant explained space and time to be merely 
" forms of perception " space the form of external, 
time of internal, sensitivity there has been a keen 
controversy, which still continues, over this important 
problem. A large section of modern metaphysicians 
have persuaded themselves that this "critical fact" 
possesses a great importance as the starting-point of 
"a purely idealist theory of knowledge," and that, con- 
sequently, the natural opinion of the ordinary healthy 
mind as to the reality of time and space is swept aside. 
This narrow and ultra - idealist conception of time 
and space has become a prolific source of error. It 
overlooks the fact that Kant only touched one side 
of the problem, the subjective side, in that theory, and 
recognized the equal validity of its objective side. 
" Time and space," he said, " have empirical reality, but 
transcendental ideality." Our modern monism is quite 
compatible with this thesis of Kant's, but not with the 
one-sided exaggeration of the subjective aspect of the 
problem ; the latter leads logically to the absurd ideal- 
ism that culminates in Berkeley's thesis, " Bodies are 
but ideas; their essence is in their perception." The 
thesis should be read thus : " Bodies are only ideas 



for my personal consciousness ; their existence is just 
as real as that of my organs of thought, the ganglionic 
cells in the gray bed of my brain, which receive the im- 
press of bodies on my sense-organs and form those 
ideas by association of the impressions. It is just 
as easy to doubt or to deny the reality of my own con- 
sciousness as to doubt that of time and space. In the 
delirium of fever, in hallucinations, in dreams, and in 
double-consciousness, I take ideas to be true which are 
merely fancies. I mistake my own personality for 
another (vide p. 185) ; Descartes' famous Cogito ergo 
sum applies no longer. On the other hand, the real- 
ity of time and space is now fully established by that 
expansion of our philosophy which we owe to the law 
of substance and to our monistic cosmogony. When 
we have happily got rid of the untenable idea of 
"empty space," there remains as the infinite "space- 
filling "-medium matter, in its two forms of ether and 
mass. So also we find a "time-filling" event in the 
eternal movement, or genetic energy, which reveals 
itself in the uninterrupted evolution of substance, in 
the perpetuum mobile of the universe. 

As a body which has been set in motion continues 
to move as long as no external agency interferes with 
it, the idea was conceived long ago of constructing an 
apparatus which should illustrate perpetual motion. 
The fact was overlooked that every movement meets 
with external impediments and gradually ceases, un- 
less a new impetus is given to it from without and a 
new force is introduced to counteract the impediments. 
Thus, for instance, a pendulum would swing back- 
ward and forward for an eternity at the same speed if 
the resistance of the atmosphere and the friction at 
the point it hangs from did not gradually deprive it of 



the mechanical kinetic energy of its motion and con- 
vert it into heat. We have to furnish it with fresh 
mechanical energy by a spring (or, as in the pendulum- 
clock, by the drag of a weight). Hence it is impossi- 
ble to construct a machine that would produce, with- 
out external aid, a surplus of energy by which it could 
keep itself going. Every attempt to make such a per- 
petuum mobile must necessarily fail; the discovery of 
the law of substance showed, in addition, the theoreti- 
cal impossibility of it. 

The case is different, however, when we turn to the 
world at large, the boundless universe that is in eternal 
movement. The infinite matter, which fills it objec- 
tively, is what we call space in our subjective impres- 
sion of it ; time is our subjective conception of its eternal 
movement, which is, objectively, a periodic, cyclic evo- 
lution. These two " forms of perception " teach us the 
infinity and eternity of the universe. That is, more- 
over, equal to saying that the universe itself is a per- 
petuum mobile. This infinite and eternal " machine 
of the universe" sustains itself in eternal and uninter- 
rupted movement, because every impediment is com- 
pensated by an " equivalence of energy," and the un- 
limited sum of kinetic and potential energy remains 
always the same. The law of the persistence of force 
proves also that the idea of a perpetuum mobile is just as 
applicable to, and as significant for, the cosmos as a 
whole as it is impossible for the isolated action of any 
part of it. Hence the theory of entropy is likewise un- 

The able founder of the mechanical theory of heat 
(1850), Clausius, embodied the momentous contents of 
this important theory in two theses. The first runs: 
" The energy of the universe is constant " that is one- 



half of our law of substance, the principle of energy 
(vide p. 230). The second thesis is: " The energy of 
the universe tends towards a maximum." In my opin- 
ion this second assertion is just as erroneous as the 
first is true. In the theory of Clausius the entire energy 
of the universe is of two kinds, one of which (heat of 
the higher degree, mechanical, electrical, chemical 
energy, etc.) is partly convertible into work, but the 
other is not ; the latter energy, already converted into 
heat and distributed in the cooler masses, is irrevo- 
cably lost as far as any further work is concerned. 
Clausius calls this unconsumed energy, which is no 
longer available for mechanical work, entropy (that is, 
force that is directed inward) ; it is continually in- 
creasing at the cost of the other half. As, therefore, 
the mechanical energy of the universe is daily being 
transformed into heat, and this cannot be reconverted 
into mechanical force, the sum of heat and energy in 
the universe must continually tend to be reduced and 
dissipated. All difference of temperature must ulti- 
mately disappear, and the completely latent heat must 
be equally distributed through one inert mass of mo- 
tionless matter. All organic life and movement must 
cease when this maximum of entropy has been reached. 
That would be a real " end of the world." 

If this theory of entropy were true, we should have 
a " beginning " corresponding to this assumed "end" 
of the world a minimum of entropy, in which the dif- 
ferences in temperature of the various parts of the cos- 
mos would be at a maximum. Both ideas are quite 
untenable in the light of our monistic and consistent 
theory of the eternal cosmogenetic process; both con- 
tradict the law of substance. There is neither begin- 
ning nor end of the world. The universe is infinite, 



and eternally in motion ; the conversion of kinetic into 
potential energy, and vicissim, goes on uninterrupted- 
ly ; and the sum of this actual and potential energy 
remains constant. The second thesis of the mechan- 
ical theory of heat contradicts the first, and so must 
be rejected. 

The representatives of the theory of entropy are 
quite correct as long as they confine themselves to dis- 
tinct processes, in which, under certain conditions, the 
latent heat cannot be reconverted into work. Thus, 
for instance, in the steam-engine the heat can only be 
converted into mechanical work when it passes from 
a warmer body (steam) into a cooler (water) ; the proc- 
ess cannot be reversed. In the world at large, however, 
quite other conditions obtain conditions which per- 
mit the reconversion of latent heat into mechanical 
work. For instance, in the collision of two heavenly 
bodies, which rush towards each other at inconceivable 
speed, enormous quantities of heat are liberated, while 
the pulverized masses are hurled and scattered about 
space. The eternal drama begins afresh the rotat- 
ing mass, the condensation of its parts, the formation 
of new meteorites, their combination into larger bodies, 
and so on. 


The history of the earth, of which we are now going 
to make a brief survey, is only a minute section of the 
history of the cosmos. Like the latter, it has been the 
object of philosophic speculation and mythological fan- 
tasy for many thousand years. Its true scientific study, 
however, is much younger; it belongs, for the most 
part, to the nineteenth century. The fact that the 
earth is a planet revolving round the sun was deter- 



mined by the system of Copernicus (1543); Galilei, 
Kepler, and other great astronomers, mathematically 
determined its distance from the sun, the laws of its 
motion, and so forth. Kant and Laplace indicated,, 
in their cosmogony, the way in which the earth had 
been developed from the parent sun. But the later 
history of the earth, the formation of its crust, the 
origin of its seas and continents, its mountains and 
deserts, was rarely made the subject of serious scien- 
tific research in the eighteenth century, and in the first 
two decades of the nineteenth. As a rule, men were 
satisfied with unreliable conjectures or with the tradi- 
tional story of creation; once more the Mosaic legend 
barred the way to an independent investigation. 

In 1822 an important work appeared, which followed 
the same method in the scientific investigation of the 
history of the earth that had already proved the most 
fertile the ontological method, or the principle of "act- 
ualism." It consists in a careful study and manipula- 
tion of actual phenomena with a view to the elucidation 
of the analogous historical processes of the past. The 
Society of Science at Gottingen had offered a prize in 
1818 for "the most searching and comprehensive in- 
quiry into the changes in the earth's crust which are 
historically demonstrable, and the application which 
may be made of a knowledge of them in the investi- 
gation of the terrestrial revolutions which lie beyond 
the range of history." This prize was obtained by 
Karl Hoff , of Gotha, for his distinguished work, History 
of the Natural Changes in the Crust of the Earth in the 
Light of Tradition (1822-34). Sir Charles Lyell then 
applied this ontological or actualistic method with great 
success to the whole province of geology; his Princi- 
ples of Geology (1830) laid the firm foundation on which 



the fabric of the history of the earth was so happily 
erected. The important geogenetic research of Alex- 
ander Humboldt, Leopold Buch, Gustav Bischof, Ed- 
ward Siiss, and other geologists, were wholly based on 
the empirical foundation and the speculative principles 
of Karl Hoff and Charles Lyell. They cleared the way 
for purely rational science in the field of geology ; they 
removed the obstacles that had been put in the path 
by mythological fancy and religious tradition, espe- 
cially by the Bible and its legends. I have already dis- 
cussed the merits of Lyell, and his relations with his 
friend Charles Darwin, in the sixteenth and seventeenth 
chapters of my Natural History of Creation, and must 
refer the reader to the standard works on geology for 
a further acquaintance with the history of the earth 
and the great progress which dynamical and historical 
geology have made during the century. 

The first division of the history of the earth must 
be a separation of inorganic and organic geogeny; 
the latter begins with the first appearance of living 
things on our planet. The earlier section, the inor- 
ganic history of the earth, ran much the same course 
as that of the other planets of our system. They were 
all cast off as rings of nebula at the equator of the ro- 
tating solar mass, and gradually condensed into inde- 
pendent bodies. After cooling down a little, the glow- 
ing ball of the earth was formed out of the gaseous mass, 
and eventually, as the heat continued to radiate out 
into space, there was formed at its surface the thin solid 
crust on which we live. When the temperature at the 
surface had gone down to a certain point, the water de- 
scended upon it from the environing clouds of steam, 
and thus the first condition was secured for the rise of 
organic life, Many million years certainly more 



than a hundred have passed since this important 
process of the formation of water took place, introducing 
the third section of cosmogony, which we call biogeny. 


The third phase of the evolution of the world opens 
with the advent of organisms on our planet, and con- 
tinues uninterrupted from that point until the present 
day. The great problems which this most interesting 
part of the earth's history suggests to us were still 
thought insoluble at the beginning of the nineteenth cen- 
tury, or, at least, so difficult hat their solution seemed to 
be extremely remote. Now, at the close of the century, 
we can affirm with legitimate pride that they have been 
substantially solved by modern biology and its theory 
of transf ormism ; indeed, many of the phenomena of 
the organic world are now interpreted on physical prin- 
ciples as completely as the familiar physical phenome- 
na of inorganic nature. The merit of making the first 
important step in this difficult path and of pointing out 
the way to the monistic solution of all the problems of 
biology must be accorded to the great French scientist, 
Jean Lamarck; it was in 1809, the year of the birth of 
Charles Darwin, that he published his famous Philo- 
sophie Zoologique. In this original work not only is 
a splendid effort made to interpret all the phenomena 
of organic life from a monistic and physical point of 
view, but the path is opened which alone leads to the 
solution of the greatest enigma of this branch of sci- 
ence the problem of the natural origin of organic spe- 
cies. Lamarck, who had an equally extensive em- 
pirical acquaintance with zoology and botany, drew 
the first sketch of the theory of descent; he showed 



that all the countless members of the plant and animal 
kingdoms have arisen by slow transformation from 
simple, common ancestral types, and that it is the 
gradual modification of forms by adaptation, in recip- 
rocal action with heredity, which has brought about 
this secular metamorphosis. 

I have fully appreciated the merit of Lamarck in the 
fifth chapter, and of Darwin in the sixth and seventh 
chapters, of the Natural History of Creation. Darwin, 
fifty years afterwards, not only gave a solid founda- 
tion to all the essential parts of the theory of descent, 
but he filled up the lacunae of Lamarck's work by his 
theory of selection. Darwin reaped abundantly the 
success that Lamarck had never seen, with all his 
merit. His epoch-making work on The Origin of Spe- 
cies by Natural Selection has transformed modern biol- 
ogy from its very foundations, in the course of the last 
forty years, and has raised it to a stage of development 
that yields to no other science in existence. Darwin is 
the Copernicus of the organic world, as I said in 1868, 
and E. du Bois-Reymond repeated fifteen years after- 


The fourth and last phase of the world's history must 
be for us men that latest period of time which has wit- 
nessed the development of our own race. Lamarck 
(1809) had already recognized that this evolution is 
only rationally conceivable c.s the outcome of a natural 
process, by "descent from the apes," our next of kin 
among the mammals. Huxley then proved, in his 
famous essay on The Place of Man in Nature, that this 

* Cf . Monism, by Ernst Haeckel. 


momentous thesis is an inevitable consequence of the 
theory of descent, and is thoroughly established by 
the facts of anatomy, embryology, and palaeontology. 
He considered this " question of all questions" to be 
substantially answered. Darwin followed with a brill- 
iant discussion of the question under many aspects in 
his Descent of Man (1871). I had myself devoted a 
special chapter to Lhis important problem of the science 
of evolution in my General Morphology (1866). In 
1874 I published my Anthropogeny, which contains 
the first attempt to trace the descent of man through 
the entire chain of his ancestry right up to the earliest 
archigonous monera ; the attempt was based equally 
on the three great "documents" of evolutionary sci- 
ence anatomy, embryology, and palaeontology. The 
progress we have made in anthropogenetic research 
during the last few years is described in the paper 
which I read on " Our Present Knowledge of the Origin 
of Man " at the International Congress of Zoologists 
at Cambridge in 1898.* 

* TJie Last Link, translated by Dr. Gadow. 



The Monism of the Cosmos Essential Unity of Organic and In- 
organic Nature Carbon-Theory The Hypothesis of Abio- 
genesis Mechanical and Purposive Causes Mechanicism 
and Teleology in Kant's Works Design in the Organic and 
Inorganic Worlds Vitalism Neovitalism Dysteleology (the 
Moral of the Rudimentary Organs) Absence of Design in, 
and Imperfection of, Nature Telic Action in Organized Bod- 
ies Its Absence in Ontogeny and Phylogeny The Platonist 
* Ideas " No Moral Order Discoverable in the History of the 
Organic World, of the Vertebrates, or of the Human Race 
Prevision Design and Chance 

of the first things to be proved by the law of 
substance is the basic fact that any natural force 
can be directly or indirectly converted into any other. 
Mechanical and chemical energy, sound and heat, light 
and electricity, are mutually convertible; they seem 
to be but different modes of one and the same funda- 
mental force or energy. Thence follows the important 
thesis of the unity of all natural forces, or, as it may 
also be expressed, the "monism of energy." This fun- 
damental principle is now generally recognized in the 
entire province of physics and chemistry, as far as it 
applies to inorganic substances. 

It seems to be otherwise with the organic world and 
its wealth of color and form. It is, of course, obvious 
that a great part of the phenomena of life may be im- 



mediately traced to mechanical and chemical energy, 
and to the effects of electricity and light. For other 
vital processes, however, especially for psychic activity 
and consciousness, such an interpretation is vigorously 
contested. Yet the modern science of evolution has 
achieved the task of constructing a bridge between 
these two apparently irreconcilable provinces. We are 
now certain that all the phenomena of organic life are 
subject to the universal law of substance no less than 
the phenomena of the inorganic universe. 

The unity of nature which necessarily follows, and 
the demolition of the earlier dualism, are certainly 
among the most valuable results of modern evolution. 
Thirty-three years ago I made an exhaustive effort to 
establish this " monism of the cosmos " and the es- 
sential unity of organic and inorganic nature by a 
thorough, critical demonstration, and a comparison of 
the accordance of these two great divisions of nature 
with regard to matter, form, and force.* A short epit- 
ome of the result is given in the fifteenth chapter of 
my Natural History of Creation. The views I put 
forward are accepted by the majority of modern scien- 
tists, but an attempt has been made in many quarters 
lately to dispute them and to maintain the old antith- 
esis of the two divisions of nature. The ablest of 
these is to be found in the recent Welt als That of the 
botanist Reinke. It defends pure cosmological dual- 
ism with admirable lucidity and consistency, and only 
goes to prove how utterly untenable the teleological 
system is that is connected therewith. According to 
the author, physical and chemical forces alone are at 
work in the entire field of inorganic nature, while in 

* General Morphology, book 2, chap. v. 
2 SS 


the organic world we find " intelligent forces/' regula- 
tive or dominant forces. The law of substance is sup- 
posed to apply to the one, but not to the other. On 
the whole, it is a question of the old antithesis of a 
mechanical and a teleological system. But before we 
go more fully into it, let us glance briefly at two other 
theories, which seem to me to be of great importance 
in the decision of that controversy the carbon-theory 
and the theory of spontaneous generation. 

Physiological chemistry has, after countless analy- 
ses, established the following five facts during the last 
forty years : 

I. No other elements are found in organic bodies 
than those of the inorganic world. 

II. The combinations of elements which are pecu- 
liar to organisms, and which are responsible for their 
vital phenomena, are compound protoplasmic sub- 
stances, of the group of albuminates. 

III. Organic life itself is a chemico-physical proc- 
ess, based on the metabolism (or interchange of mate- 
rial) of these albuminates. 

IV. The only element which is capable of building 
up these compound albuminates, in combination with 
other elements (oxygen, hydrogen, nitrogen, and sul- 
phur), is carbon. 

V. These protoplasmic compounds of carbon are 
distinguished from most other chemical combinations 
by their very intricate molecular structure, their insta- 
bility, and their jelly-like consistency. 

On the basis of these five fundamental facts the fol- 
lowing " carbon-theory " was erected thirty-three years 
ago : " The peculiar chemico-physical properties of 
carbon especially the fluidity and the facility of de- 
composition of the most elaborate albuminoid com- 



pounds of carbon are the sole and the mechanical 
causes of the specific phenomena of movement, which 
distinguish organic from inorganic substances, and 
which are called life, in the usual sense of the word " 
(see The Natural History of Creation). Although this 
" carbon-theory " is warmly disputed in some quarters, 
no better monistic theory has yet appeared to replace 
it. We have now a much better and more thorough 
knowledge of the physiological relations of cell-life, 
and of the chemistry and physics of the living proto- 
plasm, than we had thirty-three years ago, and so it is 
possible to make a more confident and effective defence 
of the carbon-theory. 

The old idea of spontaneous generation is now taken 
in many different senses. It is owing to this indis- 
tinctness of the idea, and its application to so many 
different hypotheses, that the problem is one of the most 
contentious and confused of the science of the day. I 
restrict the idea of spontaneous generation also called 
abiogenesis or archigony to the first development of 
living protoplasm out of inorganic carbonates, and dis- 
tinguish two phases in this " beginning of biogenesis" : 
(i) autogony, or the rise of the simplest protoplasmic 
substances in a formative fluid, and (2) plasmogony, 
the differentiation of individual primitive organisms 
out of these protoplasmic compounds, in the form of 
monera. I have treated this important, though diffi- 
cult, problem so exhaustively in the fifteenth chap- 
ter of my Natural History of Creation that I may con- 
tent myself here with referring to it. There is also a 
very searching and severely scientific inquiry into it 
in my General Morphology (1866). Naegeli has also 
treated the hypothesis in quite the same sense in his 
mechanico-physiological theory of descent (1884), and 



has represented it to be an indispensable thesis in any 
natural theory of evolution. I entirely agree with his 
assertion that " to reject abiogenesis is to admit a mir- 

The hypothesis of spontaneous generation and the 
allied carbon-theory are of great importance in deciding 
the long-standing conflict between the Ideological (du- 
alistic) and the mechanical (monistic) interpretation 
of phenomena. Since Darwin gave us the key to the 
monistic explanation of organization in his theory of 
selection forty years ago, it has become possible for us 
to trace the splendid variety of orderly tendencies of 
the organic world to mechanical, natural causes, just 
as we could formerly in the inorganic world alone. 
Hence the supernatural and telic forces, to which the 
scientist had had recourse, have been rendered super- 
fluous. Modern metaphysics, however, continues to 
regard the latter as indispensable and the former as 

No philosopher has done more than Immanuel Kant 
in defining the profound distinction between efficient 
and final causes, with relation to the interpretation of 
the whole cosmos. In his well-known earlier work 
on The General Natural History and Theory of the 
Heavens he made a bold attempt " to treat the consti- 
tution and the mechanical origin of the entire fabric 
of the universe according to Newtonian laws." This 
" cosmological nebular theory " was based entirely on 
the mechanical phenomena of gravitation. It was ex- 
panded and mathematically established later on by 
Laplace. When the famous French astronomer was 
asked by Napoleon I. where God, the creator and sus- 
tainer of all things, came in in his system, he clearly 
and honestly replied : " Sire, I have managed with- 


out that hypothesis." That indicated the atheistic 
character which this mechanical cosmogony shares 
with all the other inorganic sciences. This is the more 
noteworthy because the theory of Kant and Laplace 
is now almost universally accepted; every attempt to 
supersede it has failed. When atheism is denounced 
as a grave reproach, as it so often is, it is well to remem- 
ber that the reproach extends to the whole of modern 
science, in so far as it gives a purely mechanical inter- 
pretation of the inorganic world. 

Mechanicism (in the Kantian sense) alone can give 
us a true explanation of natural phenomena, for it 
traces them to their real efficient causes, to blind and 
unconscious agencies, which are determined in their 
action only by the material constitution of the bodies 
we are investigating. Kant himself emphatically 
affirms that " there can be no science without this me- 
chanicism of nature," and that the capacity of human 
reason to give a mechanical interpretation of phenom- 
ena is unlimited. But when he came subsequently to 
give an elucidation of the complex phenomena of or- 
ganic nature in his critique of the teleological system, 
he declared that these mechanical causes were inade- 
quate ; that in this we must call final causes to our as- 
sistance. It is true, he said, that even here we must 
recognize the theoretical faculty of the mind to give a 
mechanical interpretation, but its actual competence 
to do so is restricted. He grants it this capacity to 
some extent ; but for the majority of the vital processes 
(and especially for man's psychic activity) he thinks we 
are bound to postulate final causes. The remarkable 
79 of the critique of judgment bears the character- 
istic heading : " On the Necessity for the Subordi- 
nation of the Mechanical Principle to the Teleological 



in the Explanation of a Thing as a Natural End." It 
seemed to Kant so impossible to explain the orderly 
processes in the living organism without postulating 
supernatural final causes (that is, a purposive creative 
force) that he said : " It is quite certain that we cannot 
even satisfactorily understand, much less elucidate, 
the nature of an organism and its internal faculty on 
purely mechanical natural principles ; it is so certain, 
indeed, that we may confidently say, ' It is absurd for 
a man to conceive the idea even that some day a New- 
ton will arise who can explain the origin of a single 
blade of grass by natural laws which are uncontrolled 
by design' such a hope is entirely forbidden us." 
Seventy years afterwards this impossible " Newton of 
the organic world " appeared in the person of Charles 
Darwin, and achieved the great task that Kant had 
deemed impracticable. 

Since Newton (1682) formulated the law of gravi- 
tation, and Kant (1755) established " the constitution 
and mechanical origin of the entire fabric of the world 
on Newtonian laws," and Laplace (1796) provided a 
mathematical foundation for this law of cosmic me- 
chanicism, the whole of the inorganic sciences have be- 
come purely mechanical, and at the same time purely 
atheistic. Astronomy, cosmogony, geology, meteor- 
ology, and inorganic physics and chemistry are now ab- 
solutely ruled by mechanical laws on a mathematical 
foundation. The idea of " design" has wholly disap- 
peared from this vast province of science. At the close 
of the nineteenth century, now that this monistic view 
has fought its way to general recognition, no scientist 
ever asks seriously of the " purpose " of any single 
phenomenon in the whole of this great field. Is any 
astronomer likely to inquire seriously to-day into the 



purpose of planetary motion, or a mineralogist to seek 
design in the structure of a crystal? Does the phys- 
icist investigate the purpose of electric force, or the 
chemist that of atomic weight? We may confidently 
answer in the negative certainly not, in the sense 
that God, or a purposive natural force, had at some 
time created these fundamental laws of the mechan- 
ism of the universe with a definite design, and causes 
them to work daily in accordance with his rational 
will. The anthropomorphic notion of a deliberate 
architect and ruler of the world has gone forever from 
this field; the "eternal, iron laws of nature" have 
taken his place. 

But the idea of design has a very great significance 
and application in the organic world. We do undeni- 
ably perceive a purpose in the structure and in the life 
of an organism. The plant and the animal seem to be 
controlled by a definite design in the combination of 
their several parts, just as clearly as we see in the ma- 
chines which man invents and constructs ; as long as 
life continues the functions of the several organs are 
directed to definite ends, just as is the operation of the 
various parts of a machine. Hence it was quite nat- 
ural that the older nai* ve study of nature, in explaining 
the origin and activity of the living being, should pos- 
tulate a creator who had "arranged all things with 
wisdom and understanding," and had constructed each 
plant and animal according to the special purpose of 
its life. The conception of this "almighty creator of 
heaven and earth" was usually quite anthropomor- 
phic ; he created " everything after its kind." As long 
as the creator seemed to man to be of human shape, to 
think with his brain, see with his eyes, and fashion 
with his hands, it was possible to form a definite pict- 



ure of this "divine engineer" and his artistic work in 
the great workshop of creation. This was not so easy 
when the idea of God became refined, and man saw in 
his "invisible God" a creator without organs a gas- 
eous being. Still more unintelligible did these anthro- 
pomorphic ideas become when physiology substituted 
for the conscious, divine architect an unconscious, 
creative "vital force" a mysterious, purposive, nat- 
ural force, which differed from the familiar forces of 
physics and chemistry, and only took these in part, 
during life, into its service. This vitalism prevailed 
until about the middle of the nineteenth century. 
Johannes Miiller, the great Berlin physiologist, was 
the first to menace it with a destructive dose of facts. 
It is true that the distinguished biologist had him- 
self (like all others in the first half of the century) 
been educated in a belief in this vital force, and 
deemed it indispensable for an elucidation of the ulti- 
mate sources of life; nevertheless, in his classical and 
still unrivalled Manual of Physiology (1833) he gave a 
demonstrative proof that there is really nothing to be 
said for this vital force. Miiller himself, in a long 
series of remarkable observations and experiments, 
showed that most of the vital processes in the human 
organism (and in the other animals) take place ac- 
cording to physical and chemical laws, and that many 
of them are capable of mathematical determination. 
That was no less true of the animal functions of the 
muscles and nerves, and of both the higher and the 
lower sense-organs, than of the vegetal functions of 
digestion, assimilation, and circulation. Only two 
branches of the life of the organism, mental action and 
reproduction, retained any element of mystery, and 
seemed inexplicable without assuming a vital force. 



But immediately after Mullet's death such important 
discoveries and advances were made in these two 
branches that the uneasy "phantom of vital force" 
was driven from its last refuge. By a very remarkable 
coincidence Johannes Miiller died in the year 1858, 
which saw the publication of Darwin's first communi- 
cation concerning his famous theory. The theory of 
selection solved the great problem that had mastered 
Miiller the question of the origin of orderly arrange- 
ments from purely mechanical causes. 

Darwin, as we have often said, had a twofold im- 
mortal merit in the field of philosophy firstly, the 
reform of Lamarck's theory of descent, and its estab- 
lishment on the mass of facts accumulated in the 
course of the half-century; secondly, the conception 
of the theory of selection, which first revealed to us the 
true causes of the gradual formation of species. Dar- 
win was the first to point out that the "struggle for 
life " is the unconscious regulator which controls the 
reciprocal action of heredity and adaptation in the 
gradual transformation of species; it is the great "se- 
lective divinity" which, by a purely "natural choice," 
without preconceived design, creates new forms, just 
as selective man creates new types by an "artificial 
choice " with a definite design. That gave us the solu- 
tion of the great philosophic problem : " How can pur- 
posive contrivances be produced by purely mechanical 
processes without design?" Kant held the problem to 
be insoluble, although Empedocles had pointed out the 
direction of the solution two thousand years before. 
His principle of " teleological mechanism" has become 
more and more accepted of late years, and has fur- 
nished a mechanical explanation even of the finest and 
most recondite processes of organic life by " the f unc- 



tional self-production of the purposive structure." Thus 
have we got rid of the transcendental "design" of the 
teleological philosophy of the schools, which was the 
greatest obstacle to the growth of a rational and mon- 
istic conception of nature. 

Very recently, however, this ancient phantom of a 
mystic vital force, which seemed to be effectually ban- 
ished, has put in a fresh appearance ; a number of dis- 
tinguished biologists have attempted to reintroduce it 
under another name. The clearest presentation of it 
is to be found in the Welt als That, of the Kiel botanist, 
J. Reinke. He takes upon himself the defence of the 
notion of miracle, of theism, of the Mosaic story of 
creation, and of the constancy of species; he calls 
"vital forces," in opposition to physical forces, the di- 
rective or dominant forces. Other neovitalists prefer, 
in the good old anthropomorphic style, a "supreme" 
engineer, who has endowed organic substance with a 
purposive structure, directed to the realization of a 
definite plan. These curious teleological hypotheses, 
and the objections to Darwinism which generally ac- 
company them, do not call for serious scientific refu- 
tation to-day. 

Thirty-three years ago I gave the title of "dystele- 
ology" to the science of those extremely interesting 
and significant biological facts, which, in the most 
striking fashion, give a direct contradiction to the tele- 
ological idea " of the purposive arrangement of the liv- 
ing organism." * This "science of rudimentary, abor- 
tive, arrested, distorted, atrophied, and cataplastic in- 
dividuals" is based on an immense quantity of remark- 
able phenomena, which were long familiar to zoologists 

* Cf . General Morphology, vol. ii., and The Natural History of 



and botanists, but were not properly interpreted, and 
their great philosophic significance appreciated, until 

All the higher animals and plants, or, in general, 
all organisms which are not entirely simple in structure, 
but are made up of a number of organs in orderly co- 
operation, are found, on close examination, to possess 
a number of useless or inoperative members, sometimes, 
indeed, hurtful and dangerous. In the flowers of most 
plants we find, besides the actual sex-leaves that effect 
reproduction, a number of other leaf-organs which have 
no use or meaning (arrested or "miscarried" pistils, 
fruit, corona, and calix-leaves, etc.). In the two large 
and variegated classes of flying animals, birds and 
insects, there are, besides the forms which make con- 
stant use of their wings, a number of species which 
have undeveloped wings and cannot fly. In nearly 
every class of the higher animals which have eyes there 
are certain types that live in the dark ; they have eyes, 
as a rule, but undeveloped and useless for vision. In 
our own human organism we have similar useless 
rudimentary structures in the muscles of the ear, in 
the eye-lid, in the nipple and milk-gland of the male, 
and in other parts of the body ; indeed, the vermiform 
appendix of our ca3cum is not only useless, but ex- 
tremely dangerous, and inflammation of it is respon- 
sible for a number of deaths every year. 

Neither the old mystic vitalism nor the new, equally 
irrational, neovitalism can give any explanation of 
these and many other purposeless contrivances in the 
structure of the plant and the animal ; but they are very 
simple in the light of the theory of descent. It shows 
that these rudimentary organs are atrophied, owing 
to disuse. Just as our muscles, nerves, and organs 



of sense are strengthened by exercise and frequent use, 
so, on the other hand, they are liable to degenerate more 
or less by disuse or suspended exercise. But, although 
the development of the organs is promoted by exercise 
and adaptation, they by no means disappear without 
leaving a trace after neglect; the force of heredity 
retains them for many generations, and only per- 
mits their gradual disappearance after the lapse of a 
considerable time. The blind " struggle for existence 
between the organs" determines their historical dis- 
appearance, just as it effected their first origin and de- 
velopment. There is no internal "purpose" whatever 
in the drama. 

The life of the animal and the plant bears the same 
universal character of incompleteness as the life of 
man. This is directly attributable to the circumstance 
that nature organic as well as inorganic is in a per- 
ennial state of evolution, change, and transformation. 
This evolution seems on the whole at least as far as 
we can survey the development of organic life on our 
planet to be a progressive improvement, an historical 
advance from the simple to the complex, the lower to 
the higher, the imperfect to the perfect. I have proved 
in my General Morphology that this historical progress 
or gradual perfecting (teleosis) is the inevitable re- 
sult of selection, and not the outcome of a preconceived 
design. That is clear from the fact that no organism 
is perfect; even if it does perfectly adapt itself to its 
environment at a given moment, this condition would 
not last very long; the conditions of existence of the 
environment are themselves subject to perpetual change 
and they thus necessitate a continuous adaptation on 
the part of the organism. 

Under the title of Design in the Living Organism, 


the famous embryologist, Karl Ernst Baer, published 
a work in 1876 which, together with the article on Dar- 
winism which accompanied it, proved very acceptable 
to our opponents, and is still much quoted in opposition 
to evolution. It was a revival of the old teleological 
system under a new name, and we must devote a line 
of criticism to it. We must premise that, though Baer 
was a scientist of the highest order, his original monis- 
tic views were gradually marred by a tinge of mysti- 
cism with the advance of age, and he eventually be- 
came a thorough dualist. In his profound work on 
"the evolution of animals" (1828), which he himself 
entitled Observation and Experiment, these two methods 
of investigation are equally applied. By careful ob- 
servation of the various phenomena of the development 
of the animal ovum Baer succeeded in giving the first 
consistent presentation of the remarkable changes which 
take place in the growth of the vertebrate from a simple 
egg-cell. At the same time he endeavored, by far-see- 
ing comparison and keen reflection, to learn the causes 
of the transformation, and to reduce them to general 
constructive laws. He expressed the general result of 
his research in the following thesis : " The evolution of 
the individual is the story of the growth of individual- 
ity in every respect." He meant that " the one great 
thought that controls all the different aspects of ani- 
mal evolution is the same that gathered the scattered 
fragments of space into spheres and linked them into 
solar systems. This thought is no other than life it- 
self, and the words and syllables in which it finds 
utterance are the varied forms of living things." 

Baer, however, did not attain to a deeper knowledge 
of this great genetic truth and a clearer insight into 
the real efficient causes of organic evolution, because 



his attention was exclusively given to one half of evo- 
lutionary science, the science of the evolution of the 
individual, embryology, or, in a wider sense, ontogeny. 
The other half, the science of the evolution of species, 
phytogeny, was not yet in existence, although Lamarck 
had already pointed out the way to it in 1809. When 
it was established by Darwin in 1859, the aged Baer 
was no longer in a position to appreciate it ; the fruit- 
less struggle which he led against the theory of selec- 
tion clearly proved that he understood neither its real 
meaning nor its philosophic importance. Teleological 
and, subsequently, theological speculations had inca- 
pacitated the ageing scientist from appreciating this 
greatest reform of biology. The teleological observa- 
tions which he published against it in his Species and 
Studies in his eighty-fouth year are mere repetitions 
of errors which the teleology of the dualists has opposed 
to the mechanical or monistic system for more than 
two thousand years. The "telic idea" which, accord- 
ing to Baer, controls the entire evolution of the ani- 
mal from the ovum, is only another expression for the 
eternal " idea " of Plato and the entelecheia of his pupil 

Our modern biogeny gives a purely physiological ex- 
planation of the facts of embryology, in assigning the 
functions of heredity and adaptation as their causes. 
The great biogenetic law, which Baer failed to appre- 
ciate, reveals the intimate causal connection between 
the ontogenesis of the individual and the phylogenesis 
of its ancestors; the former seems to be a recapitula- 
tion of the latter. Nowhere, however, in the evolution 
of animals and plants do we find any trace of design, 
but merely the inevitable outcome of the struggle for 
existence, the blind controller, instead of the provident 



God, that effects the changes of organic forms by a mu- 
tual action of the laws of heredity and adaptation. And 
there is no more trace of " design " in the embryology 
of the individual plant, animal, or man. This ontogeny 
is but a brief epitome of phylogeny, an abbreviated and 
condensed recapitulation of it, determined by the physi- 
ological laws of heredity. 

Baer ended the preface to his classical Evolution of 
Animals (1828) with these words : " The palm will be 
awarded to the fortunate scientist who succeeds in re- 
ducing the constructive forces of the animal body to 
the general forces or life-processes of the entire world. 
The tree has not yet been planted which is to make his 
cradle." The great embryologist erred once more. 
That very year, 1828, witnessed the arrival of Charles 
Darwin at Cambridge University (for the purpose of 
studying theology!) the "fortunate scientist" who 
richly earned the palm thirty years afterwards by his 
theory of selection. 

In the philosophy of history that is, in the general 
reflections which historians make on the destinies of 
nations and the complicated course of political evolu- 
tion there still prevails the notion of a " moral order 
of the universe." Historians seek in the vivid drama 
of history a leading design, an ideal purpose, which 
has ordained one or other race or state to a special tri- 
umph, and to dominion over the others. This teleo- 
logical view of history has recently become more strong- 
ly contrasted with our monistic view in proportion as 
monism has proved to be the only possible interpreta- 
tion of inorganic nature. Throughout the whole of 
astronomy, geology, physics, and chemistry there is no 
question to-day of a " moral order," or a personal God, 
whose " hand hath disposed all things in wisdom and 
19 269 


understanding." And the same must be said of the 
entire field of biology, the whole constitution and his- 
tory of organic nature, if we set aside the question of 
man for the moment. Darwin has not only proved by 
his theory of selection that the orderly processes in the 
life and structure of animals and plants have arisen 
by mechanical laws without any preconceived design, 
but he has shown us in the " struggle for life " the pow- 
erful natural force which has exerted supreme control 
over the entire course of organic evolution for millions 
of years. It may be said that the struggle for life 
is the "survival of the fittest" or the "victory of the 
best " ; that is only correct when we regard the strong- 
est as the best (in a moral sense). Moreover, the 
whole history of the organic world goes to prove 
that, besides the predominant advance towards per- 
fection, there are at all times cases of retrogression to 
lower stages. Even Baer's notion of "design" has no 
moral feature whatever. 

Do we find a different state of things in the history 
of peoples, which man, in his anthropocentric presump- 
tion, loves to call "the history of the world"? Do we 
find in every phase of it a lofty moral principle or a wise 
ruler, guiding the destinies of nations? There can be 
but one answer in the present advanced stage of nat- 
ural and human history : No. The fate of those branch- 
es of the human family, those nations and races which 
have struggled for existence and progress for thou- 
sands of years, is determined by the same "eternal 
laws of iron" as the history of the whole organic world 
which has peopled the earth for millions of years. 

Geologists distinguish three great epochs in the or- 
ganic history of the earth, as far as we can read it in 
the monuments of the science of fossils the primary, 



secondary, and tertiary epochs. According to a recent 
calculation, the first occupied at least thirty-four mill- 
ion, the second eleven million, and the third three 
million years. The history of the family of vertebrates, 
from which our own race has sprung, unfolds clearly 
before our eyes during this long period. Three differ- 
ent stages in the evolution of the vertebrate correspond 
to the three epochs ; the fishes characterized the pri- 
mary (palaeozoic) age, the reptiles the secondary (meso- 
zoic), and the mammals the tertiary (caenozoic). Of the 
three groups the fishes rank lowest in organization, 
the reptiles come next, and the mammals take the 
highest place. We find, on nearer examination of the 
history of the three classes, that their various orders 
and families also advanced progressively during the 
three epochs towards a higher stage of perfection. 
May we consider this progressive development as the 
outcome of a conscious design or a moral order of 
the universe? Certainly not. The theory of selection 
teaches us that this organic progress, like the earlier 
organic differentiation, is an inevitable consequence of 
the struggle for existence. Thousands of beautiful and 
remarkable species of animals and plants have per- 
ished during those forty-eight million years, to give 
place to stronger competitors, and the victors in this 
struggle for life were not always the noblest or most 
perfect forms in a moral sense. 

It has been just the same with the history of human- 
ity. The splendid civilization of classical antiquity 
perished because Christianity, with its faith in a loving 
God and its hope of a better life beyond the grave, gave 
a fresh, strong impetus to the soaring human mind. 
The Papal Church quickly degenerated into a pitiful 
caricature of real Christianity, and ruthlessly scattered 



the treasures of knowledge which the Hellenic philos- 
ophy had gathered ; it gained the dominion of the world 
through the ignorance of the credulous masses. In 
time the Reformation broke the chains of this mental 
slavery, and assisted reason to secure its right once 
more. But in the new, as in the older, period the great 
struggle for existence went on in its eternal fluctuation, 
with no trace of a moral order. 

And it is just as impossible for the impartial and crit- 
ical observer to detect a " wise providence " in the fate 
of individual human beings as a moral order in the his- 
tory of peoples. Both are determined with iron neces- 
sity by a mechanical causality which connects every 
single phenomenon with one or more antecedent causes. 
Even the ancient Greeks recognized ananke, the blind 
heimarmene, the fate "that rules gods and men," as 
the supreme principle of the universe. Christianity re- 
placed it by a conscious Providence, which is not blind, 
but sees, and which governs the world in patriarchal 
fashion. The anthropomorphic character of this no- 
tion, generally closely connected with belief in a per- 
sonal God, is quite obvious. Belief in a " loving Fa- 
ther," who unceasingly guides the destinies of one bill- 
ion five hundred million men on our planet, and is 
attentive at all times to their millions of contradictory 
prayers and pious wishes, is absolutely impossible; 
that is at once perceived on laying aside the colored 
spectacles of " faith " and reflecting rationally on the 

As a rule, this belief in Providence and the tutelage 
of a "loving Father" is more intense in the modern 
civilized man just as in the uncultured savage when 
some good fortune has fallen him: an escape from 
peril of life, recovery from a severe illness, the winning 



of the first prize in a lottery, the birth of a long-delayed 
child, and so forth. When, on the other hand, a mis- 
fortune is met with, or an ardent wish is not fulfilled, 
" Providence " is forgotten. The wise ruler of the 
world slumbered or refused his blessing. 

In the extraordinary development of commerce of the 
nineteenth century the number of catastrophes and 
accidents has necessarily increased beyond all imagi- 
nation ; of that the journal is a daily witness. Thou- 
sands are killed every year by shipwreck, railway 
accidents, mine accidents, etc. Thousands slay each 
other every year in war, and the preparation for this 
wholesale massacre absorbs much the greater part of 
the revenue in the highest civilized nations, the chief 
professors of "Christian charity." And among these 
hundreds of thousands of annual victims of modern 
civilization strong, industrious, courageous workers 
predominate. Yet the talk of a "moral order" goes on. 

Since impartial study of the evolution of the world 
teaches us that there is no definite aim and no special 
purpose to be traced in it, there seems to be no alterna- 
tive but to leave everything to " blind chance." This 
reproach has been made to the transformism of La- 
marck and Darwin, as it had been to the previous 
systems of Kant and Laplace ; there are a number of 
dualist philosophers who lay great stress on it. It is, 
therefore, worth while to make a brief remark upon it. 

One group of philosophers affirms, in accordance 
with its teleological conception, that the whole cosmos 
is an orderly system, in which every phenomenon has 
its aim and purpose ; there is no such thing as chance. 
The other group, holding a mechanical theory, ex- 
presses itself thus: The development of the universe 
is a monistic mechanical process, in which we discover 



no aim or purpose whatever; what we call design in 
the organic world is a special result of biological agen- 
cies; neither in the evolution of the heavenly bodies 
nor in that of the crust of our earth do we find any trace 
of a controlling purpose all is the result of chance. 
Each party is right according to its definition of 
chance. The general law of causality, taken in con- 
junction with the law of substance, teaches us that 
every phenomenon has a mechanical cause; in this 
sense there is no such thing as chance. Yet it is not 
only lawful, but necessary, to retain the term for the 
purpose of expressing the simultaneous occurrence of 
two phenomena, which are not causally related to each 
other, but of which each has its own mechanical cause, 
independent of that of the other. Everybody knows 
that chance, in its monistic sense, plays an important 
part in the life of man and in the universe at large. 
That, however, does not prevent us from recognizing 
in each " chance" event, as we do in the evolution of 
the entire cosmos, the universal sovereignty of nat- 
ure's supreme law, the law of substance. 


The Idea of God in General Antithesis of God and the World; 
the Supernatural and Nature Theism and Pantheism 
Chief Forms of Theism Polytheism Tritheism Ampithe- 
ism Monotheism Religious Statistics Naturalistic Mono- 
theism Solarism Anthropistic Monotheism The Three 
Great Mediterranean Religions Mosaism Christianity 
The Cult of the Madonna and the Saints Papal Polytheism 
Islam Mixotheism Nature of Theism An Extramun- 
dane and Anthropomorphic God ; a Gaseous Vertebrate 
Pantheism Intramundane God (Nature) The Hylozoism of 
the Ionic Monists (Anaximander) Conflict of Pantheism and 
Christianity Spinoza Modern Monism Atheism 

COR thousands of years humanity has placed the 
last and supreme basis of all phenomena in an 
efficient cause, to which it gives the title of God (deus, 
theos). Like all general ideas, this notion of God has 
undergone a series of remarkable modifications and 
transformations in the course of the evolution of rea- 
son. Indeed, it may be said that no other idea has had 
so many metamorphoses ; for no other belief affects in 
so high a degree the chief objects of the mind and of 
rational science, as well as the deepest interests of the 
emotion and poetic fancy of the believer. 

A comparative criticism of the many different forms 
of the idea of God would be extremely interesting and 
instructive ; but we have not space for it in the present 



work. We must be content with a passing -glance at 
the most important forms of the belief and their rela- 
tion to the modern thought that has been evoked by a 
sound study of nature. For further information on 
this interesting question the reader would do well to 
consult the distinguished work of Adalbert Svoboda, 
Forms of Faith (1897). 

When we pass over the finer shades and the varie- 
gated clothing of the God-idea and confine our atten- 
tion to its chief element, we can distribute all the dif- 
ferent presentations of it in two groups the theistic 
and pantheistic group. The latter is closely connected 
with the monistic, or rational, view of things, and the 
former is associated with dualism and mysticism. 


In this view God is distinct from, and opposed to, the 
world as its creator, sustainer, and ruler. He is al- 
ways conceived in a more or less human form, as an 
organism which thinks and acts like a man only on 
a much higher scale. This anthropomorphic God, 
polyphyletically evolved by the different races, as- 
sumes an infinity of shapes in their imagination, from 
fetichism to the refined monotheistic religions of the 
present day. The chief forms of theism are polythe- 
ism, triplotheism, amphitheism, and monotheism. 

The polytheist peoples the world with a variety of 
gods and goddesses, which enter into its machinery 
more or less independently. Fetichism sees such sub- 
ordinate deities in the lifeless body of nature, in rocks, 
in water, in the air, in human productions of every 
kind (pictures, statues, etc.). Demonism sees gods in 
living organisms of every species trees, animals, and 


men. This kind of polytheism is found in innumer- 
able forms even in the lowest tribes. It reaches the 
highest stage in Hellenic polytheism, in the myths of 
ancient Greece, which still furnish the finest images to 
the modern poet and artist. At a much lower stage 
we have Catholic polytheism, in which innumerable 
" saints " (many of them of very equivocal repute) are 
venerated as subordinate divinities, and prayed to to 
exert their mediation with the supreme divinity. 

The dogma of the " Trinity," which still comprises 
three of the chief articles of faith in the creed of Chris- 
tian peoples, culminates in the notion that the one God 
of Christianity is really made up of three different per- 
sons : (i) God the Father, the omnipotent creator of heav- 
en and earth (this untenable myth was refuted long 
ago by scientific cosmogony, astronomy, and geology) ; 
(2) Jesus Christ; and (3) the Holy Ghost, a mystical 
being, over whose incomprehensible relation to the 
Father and the Son millions of Christian theologians 
have racked their brains in vain for the last nineteen 
hundred years. The Gospels, which are the only 
clear sources of this triplotheism, are very obscure as 
to the relation of these three persons to each other, and 
do not give a satisfactory answer to the question of 
their unity. On the other hand, it must be carefully 
noted what confusion this obscure and mystic dogma 
of the Trinity must necessarily cause in the minds of 
our children even in the earlier years of instruction. 
One morning they learn (in their religious instruction) 
that three times one are one, and the very next hour 
they are told in their arithmetic class that three times 
one are three. I remember well the reflection that this 
confusion led me to in my early school-days. 

For the rest, the " Trinity " is not an original ele- 


ment in Christianity ; like most of the other Christian 
dogmas, it has been borrowed from earlier religions. 
Out of the sun-worship of the Chaldean magi was 
evolved the Trinity of Ilu, the mysterious source of the 
world; its three manifestations were Anu, primeval 
chaos; Bel, the architect of the world; and Aa, the 
heavenly light, the all-enlightening wisdom. In the 
Brahmanic religion the Trimurti is also conceived as 
a "divine unity" made up of three persons Brahma 
(the creator), Vishnu (the sustainer), and Shiva (the 
destroyer). It would seem that in this and other ideas 
of a Trinity the " sacred number, three/' as such as 
a "symbolical number" has counted for something. 
The three first Christian virtues Faith, Hope, and 
Charity form a similar triad. 

According to the amphitheists, the world is ruled by 
two different gods, a good and an evil principle, God 
and the Devil. They are engaged in a perpetual strug- 
gle, like rival emperors, or pope and anti-pope. The 
condition of the world is the result of this conflict. The 
loving God, or good principle, is the source of all that 
is good and beautiful, of joy and of peace. The world 
would be perfect if His work were not continually 
thwarted by the evil principle, the Devil; this being 
is the cause of all that is bad and hateful, of contra- 
diction and of pain. 

Amphitheism is undoubtedly the most rational of 
all forms of belief in God, and the one which is least 
incompatible with a scientific view of the world. Hence 
we find it elaborated in many ancient peoples thou- 
sands of years before Christ. In ancient India Vishnu, 
the preserver, struggles with Shiva, the destroyer. In 
ancient Egypt the good Osiris is opposed by the wicked 
Typhon. The early Hebrews had a similar dualism 



of Aschera (or Keturah), the fertile mother-earth, and 
Elion (Moloch or Sethos), the stern heavenly father. 
In the Zend religion of the ancient Persians, founded 
by Zoroaster two thousand years before Christ, there 
is a perpetual struggle between Ormuzd, the good god 
of light, and Ahriman, the wicked god of darkness. 

In Christian mythology the Devil is scarcely less 
conspicuous as the adversary of the good deity, the 
tempter and seducer, the prince of hell, and lord of 
darkness. A personal devil was still an important 
element in the belief of most Christians at the begin- 
ning of the nineteenth century. Towards the middle 
of the century he was gradually eliminated by being 
progressively explained away, or he was restricted to 
the subordinate rdle he plays as Mephistopheles in 
Goethe's great drama. To-day the majority of edu- 
cated people look upon " belief in a personal devil " as 
a mediaeval superstition, while "belief in God" (that 
is, the personal, good, and loving God) is retained as 
an indispensable element of religion. Yet the one be- 
lief is just as much (or as little) justified as the other. 
In any case, the much-lamented " imperfection of our 
earthly life," the "struggle for existence," and all that 
pertains to it, are explained much more simply and 
naturally by this struggle of a good and an evil god 
than by any other form of theism. 

The dogma of the unity of God may in some re- 
spects be regarded as the simplest and most natural 
type of theism; it is popularly supposed to be the 
most widely accepted element of religion, and to pre- 
dominate in the ecclesiastical systems of civilized coun- 
tries. In reality, that is not the case, because this al- 
leged "monotheism" usually turns out on closer in- 
quiry to be one of the other forms of theism we have 



examined, a number of subordinate deities being gen- 
erally introduced besides the supreme one. Most of 
the religions which took a purely monotheistic stand- 
point have become more or less polytheistic in the 
course of time. Modern statistics assure us that of 
the one billion five hundred million men who people 
the earth the great majority are monotheists ; of these, 
nominally, about six hundred millions are Brahma- 
Buddhists, five hundred millions are called Christians, 
two hundred millions are heathens (of various types), 
one hundred and eighty millions are Mohammedans, 
ten millions are Jews, and ten millions have no re- 
ligion at all. However, the vast majority of these 
nominal monotheists have very confused ideas about 
the deity, or believe in a number of gods and god- 
desses besides the chief god angels, devils, etc. 

The different forms which monotheism has assumed 
in the course of its polyphyletic development may be 
distributed in two groups those of naturalistic and 
anthropistic monotheism. Naturalistic monotheism 
finds the embodiment of the deity in some lofty and 
dominating natural phenomenon. The sun, the deity 
of light and warmth, on whose influence all organic 
life insensibly and directly depends, was taken to be 
such a phenomenon many thousand years ago. Sun- 
worship (solarism, or heliotheism) seems to the modern 
scientist to be the best of all forms of theism, and the 
one which may be most easily reconciled with modern 
monism. For modern astrophysics and geogeny have 
taught us that the earth is a fragment detached from 
the sun, and that it will eventually return to the bosom 
of its parent. Modern physiology teaches us that the 
first source of organic life on the earth is the formation 
of protoplasm, and that this synthesis of simple inor- 



ganic substances, water, carbonic acid, and ammonia, 
only takes place under the influence of sunlight. On 
the primary evolution of he plasmodomous plants fol- 
lowed, secondarily, that of the plasmophagous animals, 
which directly or indirectly depend on them for nour- 
ishment; and the origin of the human race itself is 
only a later stage in the development of the animal 
kingdom Indeed, the whole of our bodily and mental 
life depends, in the last resort, like all other organic 
life, on the light and heat rays of the sun. Hence in 
the light of pure reason, sun-worship, as a form of nat- 
uralistic monotheism, seems to have a much better 
foundation than the anthropistic worship of Christians 
and of other monotheists who conceive their god in 
human form. As a matter of fact, the sun-worshippers 
attained, thousands of years ago, a higher intellectual 
and moral standard than most of the other theists. 
When I was in Bombay, in 1 88 1, I watched with the 
greatest sympathy the elevating rites of the pious 
Parsees, who, standing on the sea-shore, or kneeling 
on their prayer-rugs, offered their devotion to the sun 
at its rise and setting.* 

Moon -worship (lunarism and selenotheism) is of 
much less importance than sun-worship. There are 
a few uncivilized races that have adored the moon as 
their only deity, but it has generally been associated 
with a worship of the stars and the sun. 

The humanization of God, or the idea that the * Su- 
preme Being " feels, thinks, and acts like man (though 
in a higher degree), has played a most important part, 
as anthropomorphic monotheism, in the history of civ- 
ilization. The most prominent in this respect are the 

* Vide A Visit to Ceylon, E. Haeckel, translated by C. Bell. 



three great religions of the Mediterranean peoples 
the old Mosaic religion, the intermediate Christian 
religion, and the younger Mohammedanism. These 
three great Mediterranean religions, all three arising 
on the east coast of the most interesting of all seas, and 
originating in an imaginative enthusiast of the Se- 
mitic race, are intimately connected, not only by this 
external circumstance of an analogous origin, but 
by many common features of their internal contents. 
Just as Christianity borrowed a good deal of its my- 
thology directly from ancient Judaism, so Islam has 
inherited much from both its predecessors. All the 
three were originally monotheistic ; all three were sub- 
sequently overlaid with a great variety of polytheistic 
features, in proportion as they extended, first along 
the coast of the Mediterranean with its heterogeneous 
population, and eventually into every part of the world. 
The Hebrew monotheism, as it was founded by Moses 
(about 1600 B.C.), is usually regarded as the ancient 
faith which has been of the greatest importance in the 
ethical and religious development of humanity. This 
high historical appreciation is certainly valid in the 
sense that the two other world - conquering Mediter- 
ranean religions issued from it ; Christ was just as truly 
a pupil of Moses as Mohammed was afterwards of Christ. 
So also the New Testament, which has become the 
foundation of the belief of the highest civilized nations 
in the short space of nineteen hundred years, rests on 
the venerable basis of the Old Testament. The Bible, 
which the two compose, has had a greater influence and 
a wider circulation than any other book in the world. 
Even to-day the Bible in spite of its curious mingling 
of the best and the worst elements is in a certain sense 
the " book of books." Yet when we make an impar- 



tial and unprejudiced study of this notable historical 
source, we find it very different in several important 
respects from the popular impression. Here again 
modern criticism and history have come to certain con- 
clusions which destroy the prevalent tradition in its 
very foundations. 

The monotheism which Moses endeavored to estab- 
lish in the worship of Jehovah, and which the prophets 
the philosophers of the Hebrew race afterwards 
developed with great success, had at first to sustain 
a long and severe struggle with the dominant polythe- 
ism which was in possession. Jehovah, or Yahveh, 
was originally derived from the heaven-god, which, 
under the title of Moloch or Baal, was one of the most 
popular of the Oriental deities (the Sethos or Typhon 
of the Egyptians, and the Saturn or Cronos of the 
Greeks). There were, however, other gods in great 
favor with the Jewish people, and so the struggle with 
"idolatry" continued. Still, Jehovah was, in princi- 
ple, the only God, explicitly claiming, in the first pre- 
cept of the decalogue : " I am the Lord thy God ; thou 
shalt have no other gods beside me." 

Christian monotheism shared the fate of its moth- 
er, Mosaism; it was generally only monotheistic in 
theory, while it degenerated practically into every 
kind of polytheism. In point of fact, monotheism was 
logically abandoned in the very dogma of the Trinity, 
which was adopted as an indispensable foundation 
of the Christian religion. The three persons, which 
are distinguished as Father, Son, and Holy Ghost, are 
three distinct individuals (and, indeed, anthropomor- 
phic persons), just as truly as the three Indian deities 
of the Trimurti (Brahma, Vishnu, and Shiva) or the 
Trinity of the ancient Hebrews (Anu, Bel, and Aa). 



Moreover, in the most widely distributed form of Chris- 
tianity the " virgin " mother of Christ plays an impor- 
tant part as a fourth deity ; in many Catholic countries 
she is practically taken to be much more powerful and 
influential than the three male persons of the celestial 
administration. The cult of the madonna has been de- 
veloped to such an extent in these countries that we 
may oppose it to the usual masculine form of mono- 
theism as one of a feminine type. The " Queen of 
Heaven" becomes so prominent, as is seen in so many 
pictures and legends of the madonna, that the three 
male persons practically disappear. 

In addition, the imagination of the pious Christian 
soon came to increase this celestial administration by 
a numerous company of "saints" of all kinds, and 
bands of musical angels, who should see that " eternal 
life" should not prove too dull. The popes the great- 
est charla'ans that any religion ever produced have 
constantly studied to increase this band of celestial 
satellites by repeated canonizations. This curious com- 
pany received its most interesting acquisition in 1870, 
when the Vatican Council pronounced the popes, as 
the vicars of Christ, to be infallible, and thus raised 
them to a divine dignity. When we add the "personal 
Devil" that they acknowledge, and the "bad angels" 
who form his court, we have in modern Catholicism, 
still the most extensive branch of Christianity, a rich 
and variegated polytheism that dwarfs the Olympic 
family of the Greeks. 

Islam, or the Mohammedan monotheism, is the 
youngest and purest form of monotheism. When the 
young Mohammed (born 570) learned to despise the 
polytheistic idolatry of his Arabian compatriots, and 
became acquainted with Nestorian Christianity, he 



adopted its chief doctrines in a general way; but he 
could not bring himself to see anything more than a 
prophet in Christ, like Moses. He found in the dogma 
of the Trinity what every emancipated thinker finds 
on impartial reflection an absurd legend which is 
neither reconcilable with the first principles of reason 
nor of any value whatever for our religious advance- 
ment. He justly regarded the worship of the immacu- 
late mother of God as a piece of pure idolatry, like the 
veneration of pictures and images. The longer he re- 
flected on it, and the more he strove after a purified 
idea of deity, the clearer did the certitude of his great 
maxim appear : "God is the only God " there are no 
other gods beside him. 

Yet Mohammed could not free himself from the an- 
thropomorphism of the God-idea. His one only God 
was an idealized, almighty man, like the stern, vin- 
dictive God of Moses, and the gentle, loving God of 
Christ. Still, we must admit that the Mohammedan 
religion has preserved the character of pure monothe- 
ism throughout the course of its historical development 
and its inevitable division much more faithfully than 
the Mosaic and Christian religions. We see that to- 
day, even externally, in its forms of prayer and preach- 
ing, and in the architecture and adornment of its 
mosques. When I visited the East for the first time, in 
1873, and admired the noble mosques of Cairo, Smyrna, 
Brussa, and Constantinople, I was inspired with a feel- 
ing of real devotion by the simple and tasteful decora- 
tion of the interior, and the lofty and beautiful archi- 
tectural work of the exterior. How noble and inspir- 
ing do these mosques appear in comparison with the 
majority of Catholic churches, which are covered in- 
ternally with gaudy pictures and gilt, and are out- 


wardly disfigured by an immoderate crowd of human 
and animal figures! Not less elevated are the silent 
prayers and the simple devotional acts of the Koran 
when compared with the loud, unintelligible verbosity 
of the Catholic Mass and the blatant music of their 
theatrical processions. 

Under the title of mixotheism we may embrace all the 
forms of theistic belief which contain mixtures of re- 
ligious notions of different, sometimes contradictory, 
kinds. In theory this most widely diffused type of 
religion is not recognized at all; in the concrete it is 
the most important and most notable of all. The vast 
majority of men who have religious opinions have al- 
ways been, and still are, mixotheists; their idea of God 
is picturesquely compounded from the impressions re- 
ceived in childhood from their own sect, and a number 
of other impressions which are received later on, from 
contact with members of other religions, and which 
modify the earlier notions. In educated people there is 
also sometimes the modifying influence of philosophic 
studies in maturer years, and especially the unpreju- 
diced study of natural phenomena, which reveals the 
futility of the theistic idea. The conflict of these con- 
tradictory impressions, which is very painful to a sensi- 
tive soul, and which often remains undecided through- 
out- life, clearly shows the immense power of the hered- 
ity of ancient myths on the one hand and the early 
adaptation to erroneous dogmas on the other. The 
particular faith in which the child has been brought 
up generally remains in power, unless a "conversion" 
takes place subsequently, owing to the stronger influ- 
ence of some other religion. But even in this superses- 
sion of one faith by another the new name, like the old 
one, proves to be merely an outward label covering a 



mixture of the most diverse opinions and errors. The 
greater part of those who call themselves Christians 
are not monotheists (as they think), but amphitheists, 
triplotheists, or polytheists. And the same must be 
said of Islam and Mosaism, and other monotheistic 
religions. Everywhere we find associated with the 
original idea of a " sole and triune God " later beliefs 
in a number of subordinate deities angels, devils, 
saints, etc. a picturesque assortment of the most di- 
verse theistic forms. 

All the above forms of theism, in the proper sense of 
the word whether the belief assumes a naturalistic or 
an anthropistic form represent God to be an extra- 
mundane or a supernatural being. He is always op- 
posed to the world, or nature, as an independent being ; 
generally as its creator, sustainer, and ruler. In most 
religions he has the additional character of personality, 
or, to put it more definitely still, God as a person is 
likened to man. "In his gods man paints himself." 
This anthropomorphic conception of God as one 
who thinks, feels, and acts like man prevails with the 
great majority of theists, sometimes in a cruder and 
more naive form, sometimes in a more refined and 
abstract degree. In any case the form of theosophy 
we have described is sure to affirm that God, the su- 
preme being, is infinite in perfection, and therefore far 
removed from the imperfection of humanity. Yet, 
when we examine closely, we always find the same 
psychic or mental activity in the two. God feels, 
thinks, and acts as man does, although it be in an 
infinitely more perfect form. 

The personal anthropism of God has become so nat- 
ural to the majority of believers that they experience 
no shock when they find God personified in human 



form in pictures and statues, and in the varied images 
of the poet, in which God takes human form that is, 
is changed into a vertebrate. In some myths, even, 
God takes the form of other mammals (an ape, lion, 
bull, etc.), and more rarely of a bird (eagle, dove, or 
stork), or of some lower vertebrate (serpent, crocodile, 
dragon, etc.). 

In the higher and more abstract forms of religion 
this idea of bodily appearance is entirely abandoned, 
and God is adored as a "pure spirit" without a body. 
"God is a spirit, and they who worship him must 
worship him in spirit and in truth." Nevertheless, 
the psychic activity of this "pure spirit" remains just 
the same as that of the anthropomorphic God. In real- 
ity, even this immaterial spirit is not conceived to be 
incorporeal, but merely invisible, gaseous. We thus 
arrive at the paradoxical conception of God as a gaseous 


Pantheism teaches that God and the world are one. 
The idea of God is identical with that of nature or sub- 
stance. This pantheistic view is sharply opposed in 
principle to all the systems we have described, and to 
all possible forms of theism although there have been 
many attempts made from both sides to bridge over 
the deep chasm that separates the two. There is al- 
ways this fundamental contradiction between them, 
that in theism God is opposed to nature as an extramun- 
dane being, as creating and sustaining the world, and 
acting upon it from without, while in pantheism God, 
as an intramundane being, is everywhere identical 
with nature itself, and is operative within the world 
as " force " or * energy." The latter view alone is com- 



patible with our supreme law the law of substance. 
It follows necessarily that pantheism is the world- 
system of the modern scientist. There are, it is true, 
still a few men of science who contest this, and think 
it possible to reconcile the old theistic theory of human 
nature with the pantheistic truth of the law of sub- 
stance. All these efforts rest on confusion or sophistry 
when they are honest. 

As pantheism is a result of an advanced conception 
of nature in the civilized mind, it is naturally much 
younger than theism, the crudest forms of which are 
found in great variety in the uncivilized races of ten 
thousand years ago. We do, indeed, find the germs 
of pantheism in different religions at the very dawn of 
philosophy in the earliest civilized peoples (in India, 
Egypt, China, and Japan), several thousand years be- 
fore the time of Christ ; still, we do not meet a definite 
philosophical expression of it until the hylozoism of 
the Ionic philosophers, in the first half of the sixth cen- 
tury before Christ. All the great thinkers of this flour- 
ishing period of Hellenic thought are surpassed by the 
famous Anaximander, of Miletus, who conceived the 
essential unity of the infinite universe (apeiron) more 
profoundly and more clearly than his master, Thales, 
or his pupil, Anaximenes. Not only the great thought 
of the original unity of the cosmos and the development 
of all phenomena out of the all-pervading primitive 
matter found expression in Anaximander, but he even 
enunciated the bold idea of countless worlds in a peri- 
odic alternation of birth and death. 

Many other great philosophers of classical antiquity, 
especially Democritus, Heraclitus, and Empedocles, 
had, in the same or an analogous sense, a profound 
conception of this unity of nature and God, of body 



and spirit, which has obtained its highest expression 
in the law of substance of our modern monism. The 
famous Roman poet and philosopher, Lucretius Cams, 
has presented it in a highly poetic form in his poem 
"De Rerum Natura." However, this true pantheistic 
monism was soon entirely displaced by the mystic 
dualism of Plato, and especially by the powerful influ- 
ence which the idealistic philosophy obtained by its 
blending with Christian dogmas. When the papacy 
attained to its spiritual despotism over the world, pan- 
theism was hopelessly crushed; Giordano Bruno, its 
most gifted defender, was burned alive by the " Vicar 
of Christ" in the Campo dei Fiori at Rome on Feb- 
ruary 17, 1600. 

It was not until the middle of the seventeenth century 
that pantheism was exhibited in its purest form by the 
great Baruch Spinoza ; he gave for the totality of things 
a definition of substance in which God and the world 
are inseparably united. The clearness, confidence, 
and consistency of Spinoza's monistic system are the 
more remarkable when we remember that this gifted 
thinker of two hundred and fifty years ago was with- 
out the support of all those sound empirical bases which 
have been obtained in the second half of the nineteenth 
century. We have already spoken, in the first chapter, 
of Spinoza's relation to the materialism of the eigh- 
teenth and the monism of the nineteenth century. The 
propagation of his views, especially in Germany, is due, 
above all, to the immortal works of our greatest poet and 
thinker, Wolfgang Goethe. His splendid God and 
the World, Prometheus, Faust, etc., embody the great 
thoughts of pantheism in the most perfect poetic crea- 

Atheism affirms that there are no gods or goddesses, 


assuming that god means a personal, extramundane 
entity. This "godless world - system " substantially 
agrees with the monism or pantheism of the modern 
scientist; it is only another expression for it, empha- 
sizing its negative aspect, the non-existence of any su- 
pernatural deity. In this sense Schopenhauer justly 
remarks : " Pantheism is only a polite form of atheism. 
The truth of pantheism lies in its destruction of the 
dualist antithesis of God and the world, in its recog- 
nition that the world exists in virtue of its own inher- 
ent forces. The maxim of the pantheist, ' God and 
the world are one/ is merely a polite way of giving 
the Lord God his conge." 

During the whole of the Middle Ages, under the bloody 
despotism of the popes, atheism was persecuted with 
fire and sword as a most pernicious system. As the 
" godless " man is plainly identified with the " wicked " 
in the Gospel, and is threatened simply on account of 
his "want of faith" with the eternal fires of hell, it 
was very natural that every good Christian should be 
anxious to avoid the suspicion of atheism. Unfortu- 
nately, the idea still prevails very widely. The atheistic 
scientist who devotes his strength and his life to the 
search for the truth, is freely credited with all that is 
evil; the theistic church-goer, who thoughtlessly fol- 
lows the empty ceremonies of Catholic worship, is at 
once assumed to be a good citizen, even if there be no 
meaning whatever in his faith and his morality be de- 
plorable. This error will only be destroyed when, in 
the twentieth century, the prevalent superstition gives 
place to rational knowledge and to a monistic concep- 
tion of the unity of God and the world. 



The Knowledge of the Truth and Its Sources : the Activity of the 
Senses and the Association of Presentations Organs of Sense 
and Organs of Thought Sense-Organs and their Specific 
Energy Their Evolution The Philosophy of Sensibility 
Inestimable Value of the Senses Limits of Sensitive Knowl- 
edgeHypothesis and Faith Theory and Faith Essential 
Difference of Scientific (Natural) and Religious (Supernatural) 
Faith Superstition of Savage and of Civilized Races Con- 
fessions of Faith Unsectarian Schools The Faith of Our 
Fathers Spiritism Revelation 

VERY effort of genuine science makes for a knowl- 
edge of the truth. Our only real and valuable 
knowledge is a knowledge of nature itself, and con- 
sists of presentations which correspond to external 
things. We are incompetent, it is true, to penetrate 
into the innermost nature of this real world the " thing 
in itself " but impartial critical observation and com- 
parison inform us that, in the normal action of the 
brain and the organs of sense, the impressions received 
by them from the outer world are the same in all ra- 
tional men, and that in the normal function of the 
organs of thought certain presentations are formed 
which are everywhere the same. These presenta- 
tions we call true, and we are convinced that their con- 
tent corresponds to the knowable aspect of things. 
We know that these facts are not imaginary, but real. 



All knowledge of the truth depends on two different, 
but intimately connected, groups of human physio- 
logical functions: firstly, on the sense-impressions of 
the object by means of sense-action, and, secondly, on 
the combination of these impressions by an associa- 
tion into presentations in the subject. The instru- 
ments of sensation are the sense-organs (sensilla or 
aestheta) ; the instruments which form and link to- 
gether the presentations are the organs of thought 
(phroneta). The latter are part of the central, and the 
former part of the peripheral, nervous system that 
important and elaborate system of organs in the higher 
animals which alone effects their entire psychic activity. 

Man's sense-activity, which is the starting-point of 
all knowledge, has been slowly and gradually devel- 
oped from that of his nearest mammal relatives, the 
primates. The sense-organs are of substantially the 
same construction throughout this highest animal 
group, and their function takes place always according 
to the same physical and chemical laws. They have 
had the same historical development in all cases. In 
the mammals, as in the case of all other animals, the 
sensilla were originally parts of the skin ; the sensitive 
cells of the epidermis are the sources of all the differ- 
ent sense-organs, which have acquired their specific 
energy by adaptation to different stimuli (light, heat, 
sound, chemical action, etc.). The rod-cells in the ret- 
ina of the eye, the auditory cells in the cochlea of the 
ear, the olfactory cells in the nose, and the taste-cells 
on the tongue, are all originally derived from the sim- 
ple, indifferent cells of the epidermis, which cover the 
entire surface of the body. This significant fact can 
be directly proved by observation of the embryonic de- 
velopment of man or any of the higher animals. And 



from this ontogenetic fact we confidently infer, in virtue 
of the great biogenetic law, the important phylogenetic 
proposition, that in the long historical evolution of our 
ancestors, likewise, the higher sense-organs with their 
specific energies were originally derived from the epi- 
dermis of lower animals, from a simple layer of cells 
which had no trace of such differentiated sensilla. 

A particular importance attaches to the circumstance 
that different nerves are qualified to perceive different 
properties of the environment, and these only. The 
optic nerve accomplishes only the perception of light, 
the auditory nerve the perception of sound, the olfac- 
tory nerve the perception of smell, and so on. No mat- 
ter what stimuli impinge on and irritate a given sense- 
organ, its reaction is always of the same character. 
From this specific energy of the sense - nerves, which 
was first fully appreciated by Johannes Miiller, very 
erroneous inferences have been drawn, especially in 
favor of a dualistic and & priori theory of knowledge. 
It has been affirmed that the brain, or the soul, only 
perceives a certain condition of the stimulated nerve, 
and that, consequently, no conclusion can be drawn 
from the process as to the existence and nature of the 
stimulating environment. Sceptical philosophy con- 
cluded that the very existence of an outer world is 
doubtful, and extreme idealism went on positively to 
deny it, contending that things only exist in our im- 
pressions of them. 

In opposition to these erroneous views, we must re- 
call the fact that the "specific energy" was not orig- 
inally an innate, special quality of the various nerves, 
but it has arisen by adaptation to the particular ac- 
tivity of the epidermic cells in which they terminate. 
In harmony with the great law of "division of labor " 



the originally indifferent "sense-cells of the skin "un- 
dertook different tasks, one group of them taking over 
the stimulus of the light rays, another the impress of 
the sound waves, a third the chemical impulse of odor- 
ous substances, and so on. In the course of a very 
long period these external stimuli effected a gradual 
change in the physiological, and later in the morpho- 
logical, properties of these parts of the epidermis, and 
there was a correlative modification of the sensitive 
nerves which conduct the impressions they receive to 
the brain. Selection improved, step by step, such par- 
ticular modifications as proved to be useful, and thus 
eventually, in the course of many million years, cre- 
ated those wonderful instruments, the eye and the ear, 
which we prize so highly ; their structure is so remark- 
ably purposive that they might well lead to the erro- 
neous assumption of a " creation on a preconceived de- 
sign/' The peculiar character of each sense-organ and 
its specific nerve has thus been gradually evolved by 
use and exercise that is, by adaptation and has then 
been transmitted by heredity from generation to gen- 
eration. Albrecht Rau has thoroughly established this 
view in his excellent work on Sensation and Thought, 
a physiological inquiry into the nature of the human 
understanding (1896). It points out the correct sig- 
nificance of Muller's law of specific sense-energies, 
adding searching investigations into their relation to 
the brain, and in the last chapter there is an able "phi- 
losophy of sensitivity" based on the ideas of Ludwig 
Feuerbach. I thoroughly agree with his convincing 

Critical comparison of sense-action in man and the 
other vertebrates has brought to light a number of ex- 
tremely important facts, the knowledge of which we 



owe to the penetrating research of the nineteenth cen- 
tury, especially of the second half of the century. This 
is particularly true of the two most elaborate "aesthetic" 
organs, the eye and the ear. They present a different 
and more complicated structure in the vertebrates than 
in the other animals, and have also a characteristic 
development in the embryo. This typical ontogenesis 
and structure of the sensilla of all the vertebrates is 
only explained by heredity from a common ances- 
tor. Within the vertebrate group, however, we find a 
great variety of structure in points of detail, and this 
is due to adaptation to their manner of life on the part of 
the various species, to the increasing or diminishing 
use of various parts. 

In respect of the structure of his sense-organs man 
is by no means the most perfect and most highly- 
developed vertebrate. The eye of the eagle is much 
keener, and can distinguish small objects at a distance 
much more clearly than the human eye. The hearing 
of many mammals, especially of the carnivora, ungu- 
lata, and rodentia of the desert, is much more sensi- 
tive than that of man, and perceives slight noises at 
a much greater distance ; that may be seen at a glance 
by their large and very sensitive cochlea. Singing 
birds have attained a higher grade of development, 
even in respect of musical endowment, than the ma- 
jority of men. The sense of smell is much more de- 
veloped in most of the mammals, especially in the car- 
nivora and the ungulata, than in man ; if the dog could 
compare his own fine scent with that of man, he would 
look down on us with compassion. Even with regard 
to the lower senses taste, sex-sense, touch, and tem- 
perature man has by no means reached the highest 
stage in every respect. 



We can naturally only pass judgment on the sen- 
sations which we ourselves experience. However, an- 
atomy informs us of the presence in the bodies of many 
animals of other senses than those we are familiar with. 
Thus fishes and other lower aquatic vertebrates have 
peculiar sensilla in the skin which are in connection 
with special sense-nerves. On the right and left sides 
of the fish's body there is a long canal, branching into 
a number of smaller canals at the head. In this " mu- 
cous canal " there are nerves with numerous branches, 
the terminations of which are connected with peculiar 
nerve-aggregates. This extensive epidermic sense- 
organ probably serves for the perception of changes 
in the pressure, or in other properties, of the water. 
Some groups are distinguished by the possession of 
other peculiar sensilla, the meaning of which is still 
unknown to us. 

But it is already clear from the above facts that our 
human sense-activity is limited, not only in quantity, 
but in quality also. We can thus only perceive with 
our senses, especially with the eye and the sense of 
touch, a part of the qualities of the objects in our en- 
vironment. And even this partial perception is in- 
complete, in the sense that our organs are imperfect, 
and our sensory nerves, acting as interpreters, com- 
municate to the brain only a translation of the impres- 
sions received. 

However, this acknowledged imperfection of our 
senses should not prevent us from recognizing their 
instruments, and especially the eye, to be organs of 
the highest type ; together with the thought-organs in 
the brain, they are nature's most valuable gift to man. 
Very truly does Albrecht Rau say: "All science is 
sensitive knowledge in the ultimate analysis; it does 



not deny, but interpret, the data of the senses. The 
senses are our first and best friends. Long before the 
mind is developed the senses tell man what he must do 
and avoid. He who makes a general disavowal of the 
senses in order to meet their dangers acts as thought- 
lessly and as foolishly as the man who plucks out his 
eyes because they once fell on shameful things, or the 
man who cuts off his hand lest at any time it should 
reach out to the goods of his neighbor." Hence Feuer- 
bach is quite right in calling all philosophies, religions, 
and systems which oppose the principle of sense-action 
not only erroneous, but really pernicious. Without the 
senses there is no knowledge "Nihil est in intellectu, 
quod non fuerit in sensu," as Locke said. Twenty years 
ago I pointed out, in my chapter " On the Origin and 
Development of the Sense-Organs/'* the great service 
of Darwinism in giving us a profounder knowledge 
and a juster appreciation of the senses. 

The thirst for knowledge of the educated mind is 
not contented with the defective acquaintance with the 
outer world which is obtained through our imperfect 
sense-organs. He endeavors to build up the sense-im- 
pressions which they have brought him into valuable 
knowledge. He transforms them into specific sense- 
perceptions in the sense-centres of the cortex of the 
brain, and combines them into presentations, by asso- 
ciation, in the thought-centres. Finally, by a further 
concatenation of the groups of presentations he at- 
tains to connected knowledge. But this knowledge re- 
mains defective and unsatisfactory until the imagina- 
tion supplements the inadequate power of combination 
of the intelligence, and, by the association of stored-up 

* Collected Popular Lectures ; Bonn, 1878. 


images, unites the isolated elements into a connected 
whole. Thus are produced new general presentative 
images, and these suffice to interpret the facts perceived 
and satisfy "reason's feeling of causality." 

The presentations which fill up the gaps in our 
knowledge, or take its place, may be called, in a broad 
sense, "faith." That is what happens continually in 
daily life. When we are not sure about a thing wei 
say, I believe it. In this sense we are compelled to 
make use of faith even in science itself ; we conjecture 
or assume that a certain relation exists between two 
phenomena, though we do not know it for certain. If it 
is a question of a cause, we form a hypothesis; though 
in science only such hypotheses are admitted as lie 
within the sphere of human cognizance, and do not 
contradict known facts. Such hypotheses are, for in- 
stance in physics the theory of the vibratory move- 
ment of ether, in chemistry the hypothesis of atoms 
and their affinity, in biology the theory of the molecular 
structure of living protoplasm, and so forth. 

The explanation of a great number of connected phe- 
nomena by the assumption of a common cause is called 
a theory. Both in theory and hypothesis "faith" (in 
the scientific sense) is indispensable ; for here again it 
is the imagination that fills up the gaps left by the in- 
telligence in our knowledge of the connection of things. 
A theory, therefore, must always be regarded only as 
an approximation to the truth; it must be understood 
that it may be replaced in time by another and better- 
grounded theory. But, in spite of this admitted un- 
certainty, theory is indispensable for all true science; 
it elucidates facts by postulating a cause for them. 
The man who renounces theory altogether, and seeks 
to construct a pure science with certain facts alone (as 



often happens with wrong-headed representatives of 
our "exact sciences"), must give up the hope of any 
knowledge of causes, and, consequently, of the satis- 
faction of reason's demand for causality. 

The theory of gravitation in astronomy (Newton), 
the nebular theory in cosmogony (Kant and Laplace), 
the principle of energy in physics (Meyer and Helm- 
holtz), the atomic theory in chemistry (Dalton), the 
vibratory theory in optics (Huyghens), the cellular 
theory in histology (Schleiden and Schwann), and the 
theory of descent in biology (Lamarck and Darwin), 
are all important theories of the first rank; they ex- 
plain a whole world of natural phenomena by the as- 
sumption of a common cause for all the several facts of 
their respective provinces, and by showing that all the 
phenomena thereof are inter-connected and controlled 
by laws which issue from this common cause. Yet the 
cause itself may remain obscure in character, or be 
merely a " provisional hypothesis. n The " force of grav- 
ity " in the theory of gravitation and in cosmogony, 
u energy " itself in its relation to matter, the " ether " of 
optics and electricity, the " atom " of the chemist, the 
living "protoplasm" of histology, the "heredity" of 
the evolutionist these and similar conceptions of other 
great theories may be regarded by a sceptical philos- 
ophy as " mere hypotheses " and the outcome of scien- 
tific " faith/' yet they are indispensable for us, until 
they are replaced by better hypotheses. 

The dogmas which are used for the explanation of 
phenomena in the various religions, and which go by 
the name of "faith" (in the narrower sense), are of a 
very different character from the forms of scientific 
faith we have enumerated. The two types, however 
the " natural " faith of science and the " supernatural " 



faith of religion are not infrequently confounded, 
so that we must point out their fundamental differ- 
ence. Religious faith means always belief in a mira- 
cle, and as such is in hopeless contradiction with the 
natural faith of reason. In opposition to reason it pos- 
tulates supernatural agencies, and, therefore, may be 
justly called superstition. The essential difference of 
this superstition from rational faith lies in the fact that 
it assumes supernatural forces and phenomena, which 
are unknown and inadmissible to science, and which 
are the outcome of illusion and fancy; moreover, su- 
perstition contradicts the well-known laws of nature, 
and is therefore irrational. 

Owing to the great progress of ethnology during the 
century, we have learned a vast quantity of different 
kinds and practices of superstition, as they still sur- 
vive in uncivilized races. When they are compared 
with each other and with the mythological notion of 
earlier ages, a manifold analogy is discovered, fre- 
quently a common origin, and eventually one simple 
source for them all. This is found in the "demand of 
causality in reason/' in the search for an explanation 
of obscure phenomena by the discovery of a cause. 
That applies particularly to such phenomena as threat- 
en us with danger and excite fear, like thunder and 
lightning, earthquakes, eclipses, etc. The demand for 
a causal explanation of such phenomena is found in 
uncivilized races of the lowest grade, transmitted from 
their primate ancestors by heredity. It is even found 
in many other vertebrates. When a dog barks at the 
full moon, or at a ringing bell, of which it sees the ham- 
mer moving, or at a flag that flutters in the breeze, it 
expresses not only fear, but also the mysterious im- 
pulse to learn the cause of the obscure phenomenon. 

21 301 


The crude beginnings of religion among primitive races 
spring partly from this hereditary superstition of their 
primate ancestors, and partly from the worship of an- 
cestors, from various emotional impulses, and from 
habits which have become traditional. 

The religious notions of modern civilized peoples, 
which they esteem so highly, profess to be on a much 
higher level than the "crude superstition" of the sav- 
age; we are told of the great advance which civiliza- 
tion has made in sweeping it aside. That is a great 
mistake. Impartial comparison and analysis show 
that they only differ in their special "form of faith" 
and the outer shell of their creed. In the clear light of 
reason the refined faith of the most liberal ecclesiasti- 
cal religion inasmuch as it contradicts the known 
and inviolable laws of nature is no less irrational a 
superstition than the crude spirit-faith of primitive 
fetichism on which it looks down with proud disdain. 

And if, from this impartial stand-point, we take a 
critical glance at the kinds of faith that prevail to-day 
in civilized countries, we find them everywhere satu- 
rated with traditional superstition. The Christian be- 
lief in Creation, the Trinity, the Immaculate Concep- 
tion, the Redemption, the Resurrection and Ascension 
of Christ, and so forth, is just as purely imaginative as 
the belief in the various dogmas of the Mohammedan, 
Mosaic, Buddhistic, and Brahmanic religions, and is 
just as incapable of reconciliation with a rational knowl- 
edge of nature. Each of these religions is for the sin- 
cere believer an indisputable truth, and each regards 
the other as heresy and damnable error. The more 
confidently a particular sect considers itself "the only 
ark of salvation," and the more ardently this convic- 
tion is cherished, the more zealously does it contend 



against all other sects and give rise to the fearful re- 
ligious wars that form the saddest pages in the book of 
history. And all the time the unprejudiced " critique of 
pure reason" teaches us that all these different forms 
of faith are equally false and irrational, mere creatures 
of poetic fancy and uncritical tradition. Rational sci- 
ence must reject them all alike as the outcome of super- 

The incalculable injury which irrational superstition 
has done to credulous humanity is conspicuously re- 
vealed in the ceaseless conflict of confessions of faith. 
Of all the wars which nations have waged against each 
other with fire and sword the religious wars have been 
the bloodiest ; of all the forms of discord that have shat- 
tered the happiness of families and of individuals those 
that arise from religious differences are still the most 
painful. Think of the millions who have lost their 
lives in Christian persecutions, in the religious con- 
flicts of Islam and of the Reformation, by the Inquisi- 
tion, and under the charge of witchcraft. Or think of 
the still greater number of luckless men who, through 
religious differences, have been plunged into family 
troubles, have lost the esteem of their fellow-citizens 
and their position in the community, or have even been 
compelled to fly from their country. The official con- 
fession of faith becomes most pernicious of all when it is 
associated with the political aims of a modern state, and 
is enforced as "religious instruction" in our schools. 
The child's mind is thus early diverted from the pur- 
suit of the truth and impregnated with superstition. 
Every friend of humanity should do all in his power 
to promote unsectarian schools as one of the most val- 
uable institutions of the modern state. 

The great value which is, none the less, still very 


widely attached to sectarian instruction is not only due 
to the compulsion of a reactionary state and its depen- 
dence on a dominant clericalism, but also to the weight 
of old traditions and " emotional cravings " of various 
kinds. One of the strongest of these is the devout rev- 
erence which is extended everywhere to sectarian tra- 
dition, to the "faith of our fathers." In thousands of 
stories and poems fidelity to it is extolled as a spiritual 
treasure and a sacred duty. Yet a little impartial study 
of the history of faith suffices to show the absurdity of 
the notion. The dominant evangelical faith of the 
second half of the nineteenth century is essentially dif- 
ferent from that of the first half, and this again from 
that of the eighteenth century. The faith of the eigh- 
teenth century diverges considerably from the "faith 
of our fathers" of the seventeenth, and still more from 
that of the sixteenth, century. The Reformation, re- 
leasing enslaved reason from the tyranny of the popes, 
is naturally regarded by them as darkest heresy ; but 
even the faith of the papacy itself had been completely 
transformed in the course of a century. And how dif- 
ferent is the faith of the Christian from that of his heath- 
en ancestors. Every man with some degree of inde- 
pendent thought frames a more or less personal religion 
for himself, which is always different from that of his 
fathers; it depends largely on the general condition 
of thought in his day. The further we go back in 
the history of civilization, the more clearly do we find 
this esteemed " faith of our fathers " to be an indefen- 
sible superstition which is undergoing continual trans- 

One of the most remarkable forms of superstition, 
which still takes a very active part in modern life, is 
spiritism. It is a surprising and a lamentable fact 



that millions of educated people are still dominated by 
this dreary superstition ; even distinguished scientists 
are entangled in it. A number of spiritualist journals 
spread the faith far and wide, and our " superior cir- 
cles " do not scruple to hold seances in which " spirits " 
appear, rapping, writing, giving messages from " the 
beyond," and so on. It is a frequent boast of spiritists 
that even eminent men of science defend their super- 
stition. In Germany, A. Zollner and Fechner are quoted 
as instances ; in England, Wallace and Crookes. The 
regrettable circumstance that physicists and biologists 
of such distinction have been led astray by spiritism 
is accounted for, partly by their excess of imagination 
and defect of critical faculty, and partly by the power- 
ful influence of dogmas which a religious education 
imprinted on the brain in early youth. Moreover, it 
was precisely through the famous seances at Leipzig, 
in which the physicists, Zollner, Fechner, and Wilhelm 
Weber, were imposed on by the clever American con- 
juror, Slade, that the fraud of the latter was afterwards 
fully exposed ; he was discovered to be a common im- 
postor. In other cases, too, where the alleged marvels 
of spiritism have been thoroughly investigated, they 
have been traced to a more or less clever deception ; the 
mediums (generally of the weaker sex) have been found 
to be either smart swindlers or nervous persons of 
abnormal irritability. Their supposed gift of "tele- 
pathy" (or "action at a distance of thought without 
material medium") has no more existence than the 
"voices" or the "groans" of spirits, etc. The vivid 
pictures which Carl du Prel, of Munich, and other spir- 
itists give of their phenomena must be regarded as the 
outcome of a lively imagination, together with a lack 
of critical power and of knowledge of physiology. 



The majority of religions have, in spite of their great 
differences, one common feature, which is, at the same 
time, one of their strongest supports in many quarters. 
They declare that they can elucidate the problem of 
existence, the solution of which is beyond the natural 
power of reason, by the supernatural way of revelation ; 
from that they derive the authority of the dogmas which 
in the guise of " divine laws " control morality and the 
practical conduct of life. " Divine " inspirations of 
that kind form the basis of many myths and legends, 
the human origin of which is perfectly clear. It is 
true that the God who reveals himself does not always 
appear in human shape, but in thunder and lightning, 
storm and earthquake, fiery bush or menacing cloud. 
But the revelation which he is supposed to bring to the 
credulous children of men is always anthropomorphic ; 
it invariably takes the form of a communication of 
ideas or commands which are formulated and expressed 
precisely as is done in the normal action of the human 
brain and larynx. In the Indian and Egyptian re- 
ligions, in the mythologies of Greece and Rome, in the 
Old and the New Testaments, the gods think, talk, 
and act just as men do ; the revelations, in which they 
are supposed to unveil for us the secrets of existence 
and the solution of the great world-enigma, are crea- 
tions of the human imagination. The " truth " which 
the credulous discover in them is a human invention ; 
the " childlike faith " in these irrational revelations is 
mere superstition. 

The true revelation that is, the true source of ra- 
tional knowledge is to be sought in nature alone. The 
rich heritage of truth which forms the most valuable 
part of human culture is derived exclusively from the 
experiences acquired in a searching study of nature, 



and from the rational conclusions which it has reached 
by the just association of these empirical presentations. 
Every intelligent man with normal brain and senses 
finds this true revelation in nature on impartial study, 
and thus frees himself from the superstition with which 
the " revelations " of religion had burdened him. 


Increasing Opposition between Modern Science and Christian 
Theology The Old and the New Faith Defence of Rational 
Science against the Attacks of Christian Superstition, espe- 
cially against Catholicism Four Periods in the Evolution of 
Christianity : I. Primitive Christianity (the First Three Cen- 
turies) The Four Canonical Gospels The Epistles of Paul 
II. The Papacy (Ult amontane Christianity) Retrogres- 
sion of Civilization in the Middle Ages Ultramontane Falsi- 
fication of History The Papacy and Science The Papacy 
and Christianity III. The Reformation Luther and Calvin 
The Year of Emancipation IV. The Pseudo-Christianity 
of the Nineteenth Century The Papal Declaration of War 
against Reason and Science : (a) Infallibility, (6) The Encyc- 
lica, (c) The Immaculate Conception 

of the most distinctive features of the expiring 
century is the increasing vehemence of the oppo- 
sition between science and Christianity. That is both 
natural and inevitable. In the same proportion in 
which the victorious progress of modern science has 
surpassed all the scientific achievements of earlier ages 
has the untenability been proved of those mystic views 
which would subdue reason under the yoke of an al- 
leged revelation ; and the Christian religion belongs to 
that group. The more solidly modern astronomy, 
physics, and chemistry have established the sole do- 
minion of inflexible natural laws in the universe at 



large, and modern botany, zoology, and anthropology 
have proved the validity of those laws in the entire king- 
dom of organic nature, so much the more strenuously 
has the Christian religion, in association with dualistic 
metaphysics, striven to deny the application of these 
natural laws in the province of the so-called "spiritual 
life" that is, in one section of the physiology of the 

No one has more clearly, boldly, and unanswerably 
enunciated this open and irreconcilable opposition be- 
tween the modern scientific and the outworn Christian 
view than David Friedrich Strauss, the greatest theo- 
logian of the nineteenth century. His last work, The 
Old Faith and the New, is a magnificent expression of 
the honest conviction of all educated people of the pres- 
ent day who understand this unavoidable conflict be- 
tween the discredited, dominant doctrines of Christian- 
ity and the illuminating, rational revelation of modern 
science all those who have the courage to defend the 
right of reason against the pretensions of superstition, 
and who are sensible of the philosophic demand for a 
unified system of thought. Strauss, as an honorable 
and courageous free-thinker, has expounded far better 
than I could the principal points of difference between 
"the old and the new faith." The absolute irreconcil- 
ability of the opponents and the inevitability of their 
struggle ("for life or death") have been ably presented 
on the philosophic side by E. Hartmann, in his inter- 
esting work on The Self -Destruction of Christianity. 

When the works of Strauss and Feuerbach and The 
History of the Conflict between Religion and Science of 
J. W. Draper have been read, it may seem superfluous 
for us to devote a special chapter to the subject. Yet 
we think it useful, and even necessary for our purpose, 



to cast a critical glance at the historical course of this 
great struggle; especially seeing that the attacks of 
the "Church militant" on science in general, and on 
the theory of evolution in particular, have become ex- 
tremely bitter and menacing of late years. Unfortu- 
nately, the mental relaxation which has lately set in, 
and the rising flood of reaction in the political, social, 
and ecclesiastical world, are only too well calculated to 
give point to those dangers. If any one doubts it, he 
has only to look over the conduct of Christian synods 
and of the German Reichstag during the last few years. 
Quite in harmony are the recent efforts of many secular 
governments to get on as good a footing as possible 
with the "spiritual regiment," their deadly enemy 
that is, to submit to its yoke. The two forces find a 
common aim in the suppression of free thought and 
free scientific research, for the purpose of thus more 
easily securing a complete despotism. 

Let us first emphatically protest that it is a question 
for us of the necessary defence of science and reason 
against the vigorous attacks of the Christian Church 
and its vast army, not of an unprovoked attack of 
science on religion. And, in the first place, our defence 
must be prepared against Romanism or Ultramontan- 
ism. This "one ark of salvation," this Catholic Church 
" destined for all," is not only much larger and more 
powerful than the other Christian sects, but it has the 
exceptional advantage of a vast, centralized organiza- 
tion and an unrivalled political ability. Men of sci- 
ence are often heard to say that the Catholic supersti- 
tion is no more astute than the other forms of supernat- 
ural faith, and that all these insiduous institutions are 
equally inimical to reason and science. As a matter 
of general theoretical principle the statement may pass, 



but it is certainly wrong when we look to its practical 
side. The deliberate and indiscriminate attacks of the 
ultramontane Church on science, supported by the 
apathy and ignorance of the masses, are, on account 
of its powerful organization, much more severe and 
dangerous than those of other religions. 

In order to appreciate correctly the extreme impor- 
tance of Christianity in regard to the entire history of 
civilization, and particularly its fundamental oppo- 
sition to reason and science, we must briefly run over 
the principal stages of its historical evolution. It may 
be divided into four periods : (i) primitive Christianity 
(the first three centuries), (2) papal Christianity (twelve 
centuries, from the fourth to the fifteenth), (3) the Ref- 
ormation (three centuries, from the sixteenth to the 
eighteenth), and (4) modern pseudo-Christianity. 


Primitive Christianity embraces the first three cen- 
turies. Christ himself, the noble prophet and enthu- 
siast, so full of the love of humanity, was far below the 
level of classical culture; he knew nothing beyond 
the Jewish traditions; he has not left a single line of 
writing. He had, indeed, no suspicion of the advanced 
stage to which Greek philosophy and science had pro- 
gressed five hundred years before. 

All that we know of him and of his original teaching 
is taken from the chief documents of the New Testa- 
ment the four gospels and the Pauline epistles. As 
to the four canonical gospels, we now know that they 
were selected from a host of contradictory and forged 
manuscripts of the first three centuries by the three 
hundred and eighteen bishops who assembled at the 


Council of Nicaea in 327. The entire list of gospels 
numbered forty ; the canonical list contains four. As 
the contending and mutually abusive bishops could 
not agree about the choice, they determined to leave 
the selection to a miracle. They put all the books (ac- 
cording to the Synodicon of Pappus) together under- 
neath the altar, and prayed that the apocryphal books, 
of human origin, might remain there, and the genuine, 
inspired books might be miraculously placed on the 
table of the Lord. And that, says tradition, really oc- 
curred ! The three synoptic gospels (Matthew, Mark, 
and Luke all written after them, not by them, at the 
beginning of the second century) and the very different 
fourth gospel (ostensibly "after" John, written about 
the middle of the second century) leaped on the table, 
and were thenceforth recognized as the inspired (with 
their thousand mutual contradictions) foundations of 
Christian doctrine. If any modern "unbeliever" finds 
this story of the " leap of the sacred books " incredible, 
we must remind him that it is just as credible as the 
table-turning and spirit-rapping that are believed to 
take place to-day by millions of educated people ; and 
that hundreds of millions of Christians believe just as 
implicitly in their personal immortality,* their "resur- 
rection from the dead," and the Trinity of God dog- 
mas that contradict pure reason no more and no less 
than that miraculous bound of the gospel manuscripts. 
The most important sources after the gospels are the 
fourteen separate (and generaFy forged) epistles of 
Paul. The genuine Pauline epistles (three in number, 
according to recent criticism to the Romans, Gala- 
tians, and Corinthians) were written before the canoni- 
cal gospels, and contain less incredible miraculous mat- 
ter than they. They are also more concerned than the 



gospels to adjust themselves with a rational view of 
the world. Hence the advanced theology of modern 
times constructs its "ideal Christianity" rather on the 
base of the Pauline epistles than on the gospels, so 
that it has been called "Paulinism." 

The remarkable personality of Paul, who possessed 
much more culture and practical sense than Christ, is 
extremely interesting, from the anthropological point 
of view, from the fact that the racial origin of the two 
great religious founders is very much the same. Re- 
cent historical investigation teaches that Paul's father 
was of Greek nationality, and his mother of Jewish.* 
The half-breeds of these two races, which are so very 
distant in origin (although they are branches of the 
same species, the homo mediterraneus) , are often dis- 
tinguished by a happy blending of talents and tem- 
perament, as we find in many recent and actual in- 
stances. The plastic Oriental imagination and the 
critical Western reason often admirably combine and 
complete each other. That is visible in the Pauline 
teaching, which soon obtained a greater influence than 
the earliest Christian notions. Hence it is not incor- 
rect to consider Paulinism a new phenomenon, of which 
the father was the philosophy of the Greeks, and the 
mother the religion of the Jews. Neoplatonism is an 
analogous combination. 

As to the real teaching and aims of Christ (and as 
to many important aspects of his life) the views of con- 
flicting theologians diverge more and more, as histori- 
cal criticism (Strauss, Feuerbach, Baur, Renan, etc.) 
puts the accessible facts in their true light, and draws 
impartial conclusions from them. Two things, cer- 

* As to the Greek paternity of Christ, vide p. 328. 


tainly, remain beyond dispute the lofty principle of 
universal charity and the fundamental maxim of ethics, 
the * golden rule/' that issues therefrom; both, how- 
ever, existed in theory and in practice centuries before 
the time of Christ (cf. chap. xix.). For the rest, the 
Christians of the early centuries were generally pure 
Communists, sometimes " Social Democrats," who, ac- 
cording to the prevailing theory in Germany to-day, 
ought to have been exterminated with fire and sword. 


Latin Christianity, variously called Papistry, Ro- 
manism, Vaticanism, Ultramontanism, or the Roman 
Catholic Church, is one of the most remarkable phe- 
nomena in the history of civilized man ; in spite of the 
storms that have swept over it, it still exerts a most pow- 
erful influence. Of the four hundred and ten million 
Christians who are scattered over the earth the majori- 
ty that is, two hundred and twenty-five millions 
are Roman Catholics; there are seventy-five million 
Greek Catholics and one hundred and ten million 
Protestants. During a period of one thousand two 
hundred years, from the fourth to the sixteenth cen- 
tury, the papacy has almost absolutely controlled and 
tainted the spiritual life of Europe ; on the other hand, 
it has won but little territory from the ancient religions 
of Asia and Africa. In Asia Buddhism still counts 
five hundred and three million followers, the Brah- 
manic religion one hundred and thirty- eight millions, 
and Islam one hundred and twenty millions. 

It is the despotism of the papacy that lent its darkest 
character to the Middle Ages; it meant death to all 
freedom of mental life, decay to all science, corruption 


to all morality. From the noble height to which the 
life of the human mind had attained in classical an- 
tiquity, in the centuries before Christ and the first cen- 
tury after Christ, it soon sank, under the rule of the 
papacy, to a level which, in respect of the knowledge of 
the truth, can only be termed barbarism. It is often 
protested that other aspects of mental life poetry and 
architecture, scholastic learning and patristic philos- 
ophy were richly developed in the Middle Ages. But 
this activity was in the service of the Church; it did 
not tend to the cultivation, but to the suppression, of 
free mental research. The exclusive preparing for an 
unknown eternity beyond the tomb, the contempt of 
nature, the withdrawal from the study of it, which are 
essential elements of Christianity, were urged as a 
sacred duty by the Roman hierarchy. It was not until 
the beginning of the sixteenth century that a change 
for the better came in with the Reformation. 

It is impossible for us here to describe the pitiful ret- 
rogression of culture and morality during the twelve 
centuries of the spiritual despotism of Rome. It is very 
pith'ly expressed in a saying of the -greatest and the 
ablest of the Hohenzollerns ; Frederick the Great con- 
densed his judgment in the phrase that the study of his- 
tory led one to think that from Constantine to the date 
of the Reformation the whole world was insane. L. 
Biichner has given us an admirable, brief description 
of this "period of insanity" in his work on Religious 
and Scientific Systems. The reader who desires a closer 
acquaintance with the subject would do well to consult 
the historical works of Ranke, Draper, Kolb, Svoboda, 
etc. The truthful description of the awful condition of 
the Christian Middle Ages, which is given by these and 
other unprejudiced historians, is confirmed by all the 



reliable sources of investigation, and by the historical 
monuments which have come down from the saddest 
period of human history. Educated Catholics, who are 
sincere truth-seekers, cannot be too frequently recom- 
mended to study these historical sources for themselves. 
This is the more necessary as ultramontane literature 
has still a considerable influence. The old trick of de- 
ceiving the faithful by a complete reversal of facts and 
an invention of miraculous circumstances is still work- 
ed by it with great success. We will only mention 
Lourdes and the " Holy Coat " of Treves. The ultra- 
montane professor of history at Frankfurt, Johannes 
Janssen, affords a striking example of the length they 
will go in distorting historical truth; his much-read 
works (especially his History of the German People 
since the Middle Ages) are marred by falsification to an 
incredible extent. The untruthfulness of these Jesu- 
itical productions is on a level with the credulity and 
the uncritical judgment of the simple German nation 
that takes them for gospel. 

One of the most interesting of the historical facts 
which clearly prove the evil of the ultramontane des- 
potism is its vigorous and consistent struggle with sci- 
ence. This was determined on, in principle, from the 
very beginning of Christianity, inasmuch as it set faith 
above reason and preached the blind subjection of the 
one to the other; that was natural, seeing that our 
whole life on earth was held to be only a preparation 
for the legendary life beyond, and thus scientific re- 
search was robbed of any real value. The deliberate 
and successful attack on science began in the early 
part of the fourth century, particularly after the Coun- 
cil of Nicaea (327), presided over by Constantine called 
the "Great" because he raised Christianity to the po- 



sition of a state religion, and founded Constantinople, 
though a worthless character, a false-hearted hypo- 
crite, and a murderer. The success of the papacy in its 
conflict with independent scientific thought and in- 
quiry is best seen in the distressing condition of sci- 
ence and its literature during the Middle Ages. Not 
only were the rich literary treasures that classical an- 
tiquity had bequeathed to the world destroyed for the 
most part, or withdrawn from circulation, but the rack 
and the stake insured the silence of every heretic 
that is, every independent thinker. If he did not keep 
his thoughts to himself, he had to look forward to being 
burned alive, as was the fate of the great monistic phi- 
losopher, Giordano Bruno, the reformer, John Huss,and 
more than a hundred thousand other " witnesses to the 
truth." The history of science in the Middle Ages 
teaches us on every page that independent thought 
and empirical research were completely buried for 
twelve sad centuries under the oppression of the om- 
nipotent papacy. 

All that we esteem in true Christianity, in the sense 
of its founder and of his noblest followers, and that we 
must endeavor to save from the inevitable wreck of this 
great world religion for our new monistic religion, lies 
on its ethical and social planes. The principles of true 
humanism, the golden rule, the spirit of tolerance, the 
love of man, in the best and highest sense of the word 
all these true graces of Christianity were not, indeed, 
first discovered and given to the world by that religion, 
but were successfully developed in the critical period 
when classical antiquity was hastening to its doom. 
The papacy, however, has attempted to convert all 
those virtues into the direct contrary, and still to hang 
out the sign of the old firm. Instead of Christian char- 


ky, it introduced a fanatical hatred of the followers of 
all other religions ; with fire and sword it has pursued, 
not only the heathen, but every Christian sect that 
dared resist the imposition of ultramontane dogma. 
Tribunals for heretics were erected all over Europe, 
yielding unnumbered victims, whose torments seemed 
only to fill their persecutors, with all their Christian 
charity, with a peculiar satisfaction. The power of 
Rome was directed mercilessly for centuries against 
everything that stood in its way. Under the notorious 
Torquemada (1481-98), in Spain alone eight thousand 
heretics were burned alive and ninety thousand pun- 
ished with the confiscation of their goods and the 
most grievous ecclesiastical fines ; in the Netherlands, 
under the rule of Charles V., at least fifty thousand 
men fell victims to the clerical bloodthirst. And while 
the heavens resounded with the cry of the martyrs, the 
wealth of half the world was pouring into Rome, to 
which the whole of Christianity paid tribute, and the 
self-styled representatives of God on earth and their 
accomplices (not infrequently Atheists themselves) wal- 
lowed in pleasure and vice of every description. "And 
all these privileges," said the frivolous, syphilitic Pope, 
Leo X., "have been secured to us by the fable of Jesus 

Yet, with all the discipline of the Church and the 
fear of God, the condition of European society was 
pitiable. Feudalism, serfdom, the grace of God, and 
the favor of the monks ruled the land ; the poor helots 
were only too glad to be permitted to raise their mis- 
erable huts under the shadow of the castle or the clois- 
ter, their secular and spiritual oppressors and exploit- 
ers. Even to-day we suffer from the aftermath of these 
awful ages and conditions, in which there was no ques- 



tion of care for science or higher mental culture save 
in rare circumstances and in secret. Ignorance, pov- 
erty, and superstition combined with the immoral op- 
eration of the law of celibacy, which had been intro- 
duced in the eleventh century, to consolidate the ever- 
growing power of the papacy. It has been calculated 
that there were more than ten million victims of fa- 
natical religious hatred during this " Golden Age" of 
papal domination; and how many more million hu- 
man victims must be put to the account of celibacy, 
oral confession, and moral constraint, the most per- 
nicious and accursed institutions of the papal despot- 
ism! Unbelieving philosophers, who have collected 
disproofs of the existence of God, have overlooked one 
of the strongest arguments in that sense the fact that 
the Roman " Vicar of Christ " could for twelve centu- 
ries perpetrate with impunity the most shameful and 
horrible deeds "in the name of God." 


The history of civilization, which we are so fond of 
calling "the history of the world," enters upon its third 
period with the Reformation of the Christian Church, 
just as its second period begins with the founding of 
Christianity. With the Reformation begins the new 
birth of fettered reason, the reawakening of science, 
which the iron hand of the Christian papacy had re- 
lentlessly crushed for twelve hundred years. At the 
same time the spread of general education had already 
commenced, owing to the invention of printing about 
the middle of the fifteenth century; and towards its 
close several great events occurred, especially the dis- 
covery of America in 1492, which prepared the way for 


the "renaissance " of science in company with that of art. 
Indeed, certain very important advances were made in 
the knowledge of nature during the first half of the six- 
teenth century, which shook the prevailing system to 
its very foundations. Such were the circumnaviga- 
tion of the globe by Magellan in 1522, which afforded 
empirical proof of its rotundity, and the founding of 
the new system of the world by Copernicus in 1543. 

Yet the 3ist of October in the year 1517, the day on 
which Martin Luther nailed his ninety-five theses to 
the wooden door of Wittenburg Cathedral, must be 
regarded as the commencement of a new epoch; for 
on that day was forced the iron door of the prison in 
which the Papal Church had detained fettered reason 
for twelve hundred years. The merits of the great re- 
former have been partly exaggerated, partly underesti- 
mated. It has been justly pointed out that Luther, like 
all the other reformers, remained in manifold subjection 
to the deepest superstition. Thus he was throughout 
life a supporter of the rigid dogma of the verbal inspi- 
ration of the Bible; he zealously maintained the doc- 
trines of the resurrection, original sin, predestination, 
justification by faith, etc. He rejected as folly the 
great discovery of Copernicus, because in the Bible 
" Joshua bade the sun, not the earth, stand still." He 
utterly failed to appreciate the great political revolu- 
tions of his time, especially the profound and just agi- 
tation of the peasantry. Worse still was the fanatical 
Calvin, of Geneva, who had the talented Spanish phy- 
sician, Serveto, burned alive in 1553, because he re- 
jected the absurd dogma of the Trinity. The fanati- 
cal "true believers" of the reformed Church followed 
only too frequently in the blood-stained footsteps of 
their papal enemies ; as they do even in our own day. 



Deeds of unparalleled cruelty followed in the train of 
the Reformation the massacre of St. Bartholomew 
and the persecution of the Huguenots in France, bloody 
heretic-hunts in Italy, civil war in England, and the 
Thirty Years War in Germany. Yet, in spite of those 
grave blemishes, to the sixteenth and seventeenth cen- 
turies belongs the honor of once more opening a free 
path to the thoughtful mind, and delivering reason 
from the oppressive yoke of the papacy. Thus only 
was made possible that great development of different 
tendencies in critical philosophy and of new paths in sci- 
ence which won for the subsequent eighteenth century 
the honorable title of * the century of enlightenment." 


As the fourth and last stage in the history of Chris- 
tianity we oppose our nineteenth century to all its prede- 
cessors. It is true that the enlightenment of preceding 
centuries had promoted critical thought in every direc- 
tion, and the rise of science itself had furnished pow- 
erful empirical weapons; yet it seems to us that our 
progress along both lines has been quite phenomenal 
during the nineteenth century. It has inaugurated 
an entirely new period in the history of the human mind, 
characterized by the development of the monistic phi- 
losophy of nature. At its very commencement the 
foundations were laid of a new anthropology (by the 
comparative anatomy of Cuvier) and of a new biology 
(by the Philosophic Zoologique of Lamarck). The two 
great French scientists were quickly succeeded by two 
contemporary German scholars Baer, the founder 
of the science of evolution, and Johannes Miiller, the 



founder of comparative morphology and physiology. 
A pupil of Miiller, Theodor Schwann, created the far- 
reaching cellular theory in 1838, in conjunction with 
M. Schleiden. Lyell had already traced the evolution 
of the earth to natural causes, and thus proved the ap- 
plication to our planet of the mechanical cosmogony 
which Kant had sketched with so much insight in 1755. 
Finally, Robert Mayer and Helmholtz established the 
principle of energy in 1842 the second, complement- 
ary half of the great law of substance, the first half 
of which (the persistence of matter) had been previous- 
ly discovered by Lavoisier. Forty years ago Charles 
Darwin crowned all these profound revelations of the 
intimate nature of the universe by his new theory of 
evolution, the greatest natural -philosophical achieve- 
ment of our century. 

What is the relation of modern Christianity to this 
vast and unparalleled progress of science? In the first 
place, the deep gulf between its two great branches, 
conservative Romanism and progressive Protestant- 
ism, has naturally widened. The ultramontane clergy 
(and we must associate with them the orthodox " evan- 
gelical alliance ") had naturally to offer a strenuous 
opposition to this rapid advance of the emancipated 
mind; they continued unmoved in their rigid literal 
^belief, demanding the unconditional surrender of rea- 
son to dogma. Liberal Protestantism, on the other 
hand, took refuge in a kind of monistic pantheism, and 
sought a means of reconciling two contradictory prin- 
ciples. It endeavored to combine the unavoidable 
recognition of the established laws of nature, and the 
philosophic conclusions that followed from them, with 
a purified form of religion, in which scarcely anything 
remained of the distinctive teaching of faith. There 



were many attempts at compromise to be found between 
the two extremes; but the conviction rapidly spread 
that dogmatic Christianity had lost every foundation, 
and that only its valuable ethical contents should be 
saved for the new monistic religion of the twentieth 
century. As, however, the existing external forms 
of the dominant Christian religion remained unaltered, 
and as, in spite of a progressive political development, 
they are more intimately than ever connected with the 
practical needs of the State, there has arisen that wide- 
spread religious profession in educated spheres which 
we can only call " pseudo-Christianity " at the bot- 
tom it is a " religious lie " of the worst character. The 
great dangers which attend this conflict between sin- 
cere conviction and the hypocritical profession of mod- 
ern pseudo-Christians are admirably described in Max 
Nordau's interesting work on The Conventional Lies 
of Civilization. 

In the midst of this obvious falseness of prevalent 
pseudo-Christianity there is one favorable circumstance 
for the progress of a rational study of nature : its most 
powerful and bitterest enemy, the Roman Church, 
threw off its mask of ostensible concern for higher men- 
tal development about the middle of the nineteenth 
century, and declared a guerre a I'outrance against in- 
dependent science. This happened in three important 
challenges to reason, for the explicitness and resolute- 
ness of which modern science and culture cannot but 
be grateful to the " Vicar of Christ." (i) In Decem- 
ber, 1854, the pope promulgated the dogma of the im- 
maculate conception of Mary. (2) Ten years after- 
wards in December, 1864 the pope published, in 
his famous encyclica, an absolute condemnation of the 
whole of modern civilization and culture ; in the sylla- 

3 2 3 


that accompanied it he enumerated and anathe- 
matized all the rational theses and philosophical prin- 
ciples which are regarded by modern science as lucid 
truths. (3) Finally, six years afterwards on July 
13, 1870 the militant head of the Church crowned 
his folly by claiming infallibility for himself and all 
his predecessors in the papal chair. This triumph 
of the Roman curia was communicated to the aston- 
ished world five days afterwards, on the very day on 
which France declared war with Prussia. Two months 
later the temporal power of the pope was taken from 
him in consequence of the war. 

These three stupendous acts of the papacy were such 
obvious assaults on the reason of the nineteenth cen- 
tury that they gave rise, from the very beginning, to 
a most heated discussion even within orthodox Catho- 
lic circles. When the Vatican Council proceeded to 
define the dogma of infallibility on July 13, 1870, 
only three-fourths of the bishops declared in its favor, 
451 out of 601 assenting; many other bishops, who 
wished to keep clear of the perilous definition, were ab- 
sent from the council. But the shrewd pontiff had 
calculated better than the timid " discreet Catholics " : 
even this extraordinary dogma was blindly accepted by 
the credulous and uneducated masses of the faithful. 

The whole history of the papacy, as it is substanti- 
ated by a thousand reliable sources and accessible doc- 
uments, appears to the impartial student as an un- 
scrupulous tissue of lying and deceit, a reckless pur- 
suit of absolute mental despotism and secular power, 
a frivolous contradiction of all the high moral pre- 
cepts which true Christianity enunciates charity and 
toleration, truth and chastity, poverty and self-denial. 
When we judge the long series of popes and of the Ro< 



man princes of the Church, from whom the pope is 
chosen, by the standard of pure Christian morality, 
it is clear that the great majority of them were pitiful 
impostors, many of them utterly worthless and vicious. 
These well-known historical facts, however, do not 
prevent millions of educated Catholics from admitting 
the infallibility which the pope has claimed for himself ; 
they do not prevent Protestant princes from going to 
Rome, and doing reverence to the pontiff (their most 
dangerous enemy) ; they do not prevent the fate of the 
German people from being intrusted to-day to the hands 
of the servants and followers of this * pious impostor " 
in the Reichstag thanks to the incredible political 
indolence and credulity of the nation. 

The most interesting of the three great events by 
which ttie papacy has endeavored to maintain and 
strengthen its despotism in the nineteenth century is 
the publication of the encyclica and the syllabus in 
December, 1864. In these remarkable documents all 
independent action was forbidden to reason and science, 
and they were commanded to submit implicitly to faith 
that is, to the decrees of the infallible pope. The 
great excitement which followed this sublime piece of 
effrontery in educated and independent circles was in 
proportion with the stupendous contents of the ency- 
clica. Draper has given us an excellent discussion 
of its educational and political significance in his His- 
tory of the Conflict between Science and Religion. 

The dogma of the immaculate conception seems, 
perhaps, to be less audacious and significant than the 
encyclica and the dogma of the infallibility of the pope. 
Yet not only the Roman hierarchy, but even some of 
the orthodox Protestants (the Evangelical Alliance, 
for instance), attach great importance to this thesis. 



What is known as the " immaculate oath " that is, 
the confirmation of faith by an oath taken on the im- 
maculate conception of Mary is still regarded by mill- 
ions of Christians as a sacred obligation. Many 
believers take the dogma in a twofold application; 
they think that the mother of Mary was impregnated 
by the Holy Ghost as well as Mary herself. Compara- 
tive and critical theology has recently shown that this 
myth has no greater claim to originality than most of 
the other stories in the Christian mythology; it has 
been borrowed from older religions, especially Buddhism. 
Similar myths were widely circulated in India, Persia, 
Asia Minor, and Greece several centuries before the 
birth of Christ. Whenever a king's unwedded daugh- 
ter, or some other maid of high degree, gave birth to a 
child, the father was always pronounced to be a god, 
or a demi-god; in the Christian case it was the Holy 

The special endowments of mind or body which often 
distinguished these " children of love " above ordinary 
offspring were thus partly explained by " heredity." 
Distinguished " sons of God " of this kind were held in 
high esteem both in antiquity and during the Middle 
Ages, while the moral code of modern civilization re- 
proaches them with their want of honorable parentage. 
This applies even more forcibly to " daughters of God," 
though the poor maidens are just as little to blame for 
their want of a father. For the rest, every one who is 
familiar with the beautiful mythology of classical an- 
tiquity knows that these sons and daughters of the 
Greek and Roman gods often approach nearest to the 
highest ideal of humanity. Recollect the large legiti- 
mate family, and the still more numerous illegitimate 
offspring, of Zeus. 



To return to the particular question of the impreg- 
nation of the Virgin Mary by the Holy Ghost, we are 
referred to the gospels for testimony to the fact. The 
only two evangelists who speak of it, Matthew and 
Luke, relate in harmony that the Jewish maiden Mary 
was betrothed to the carpenter Joseph, but became preg- 
nant without his co-operation, and, indeed, "by the Holy 
Ghost." As we have already related, the four canonical 
gospels which are regarded as the only genuine ones by 
the Christian Church, and adopted as the foundation of 
faith, were deliberately chosen from a much larger num- 
ber of gospels, the details of which contradict each other 
sometimes just as freely as the assertions of the four. 
The fathers of the Church enumerate from forty to fifty 
of these spurious or apocryphal gospels ; some of them 
are written both in Greek and Latin for instance, the 
gospel of James, of Thomas, of Nicodemus, and so 
forth. The details which these apocryphal gospels 
give of the life of Christ, especially with regard to his 
birth and childhood, have just as much (or, on the 
whole, just as little) claim to historical validity as the 
four canonical gospels. 

Now we find in one of these documents an historical 
statement, confirmed, moreover, in the Sepher Toldoth 
Jeschua, which probably furnishes the simple and nat- 
ural solution of the " world-riddle " of the supernatural 
conception and birth of Christ. The author curtly 
gives us in one sentence the remarkable statement 
which contains this solution: "Josephus Pandera, the 
Roman officer of a Calabrian legion ^ which was in 
Judaea, seduced Miriam of Bethlehem, and was the 
father of Jesus." Other details given about Miriam 
(the Hebrew name for Mary) are far from being to the 
credit of the " Queen of Heaven." 



Naturally, these historical details are carefully avoid- 
ed by the official theologian, but they assort badly with 
the traditional myth, and lift the veil from its mystery 
in a very simple and natural fashion. That makes it 
the more incumbent on impartial research and pure 
reason to make a critical examination of these state- 
ments. It must be admitted that they have much more 
title to credence than all the other statements about the 
birth of Christ. When, on familiar principles of science, 
we put aside the notion of supernatural conception 
through an "overshadowing of the Most High" as a 
pure myth, there only remains the widely accepted ver- 
sion of modern rational theology that Joseph, the 
Jewish carpenter, was the true father of Christ. But 
this assumption is explicitly contradicted by many 
texts of the gospels ; Christ himself was convinced that 
he was a " Son of God," and he never recognized his 
foster-father, Joseph, as his real parent. Joseph, indeed, 
wanted to leave his betrothed when he found her preg- 
nant without his interference. He gave up this idea 
when an angel appeared to him in a dream and paci- 
fied him. As it is expressly stated in the first chapter 
of Matthew (vv. 24, 25), there was no sexual intercourse 
between Joseph and Mary until after Jesus was born. 

The statement of the apocryphal gospels, that the 
Roman officer, Pandera, was the true father of Christ, 
seems all the more credible when we make a careful 
anthropological study of the personality of Christ. He 
is generally regarded as purely Jewish. Yet the char- 
acteristics which distinguish his high and noble person- 
ality, and which give a distinct impress to his religion, 
are certainly not Semitical ; they are rather features of 
the higher Arian race, and especially of its noblest 
branch, the Hellenes. Now, the name of Christ's real 



father, " Pander a," points unequivocally to a Greek 
origin ; in one manuscript, in fact, it is written * Pan- 
dora." Pandora was, according to the Greek mythol- 
ogy, the first woman, born of the earth by Vulcan and 
adorned with every charm by the gods, who was es- 
poused by Epimetheus, and sent by Zeus to men with 
the dread " Pandora - box, " containing every evil, in 
punishment for the stealing of divine fire from heaven 
by Prometheus. 

And it is interesting to see the different reception that 
the love-story of Miriam has met with at the hands of 
the four great Christian nations of civilized Europe. 
The stern morality of the Teutonic races entirely repu- 
diates it ; the righteous German and the prudish Briton 
prefer to believe blindly in the impossible thesis of a 
conception * by the Holy Ghost." It is well known 
that this strenuous and carefully paraded prudery of 
the higher classes (especially in England) is by no 
means reflected in the true condition of sexual morality 
in high quarters. The revelations which the Pall 
Mall Gazette, for instance, made on the subject twelve 
years ago vividly recalled the condition of Babylon. 

The Romantic races, which ridicule this prudery and 
take sexual relations less seriously, find Mary's Ro- 
mance attractive enough ; the special cult which " Our 
Lady " enjoys in France and Italy is often associated 
with this love-story with curious naivete". Thus, for 
example, Paul de Regla (Dr. Desjardin), author of Jesus 
of Nazareth considered from a Scientific, Historical, and 
Social Standpoint (1894), finds precisely in the illegiti- 
mate birth of Christ a special * title to the halo that ir- 
radiates his noble form." 

It seemed to me necessary to enter fully into this im- 
portant question of the origin of Christ in the sense of 



impartial historical science, because the Church mili- 
tant itself lays great emphasis on it, and because it re- 
gards the miraculous structure which has been founded 
on it as one of its strongest weapons against modern 
thought. The highest ethical value of pure primitive 
Christianity and the ennobling influence of this "re- 
ligion of love" on the history of civilization are quite 
independent of those mythical dogmas. The so-called 
"revelations" on which these myths are based are in- 
compatible with the firmest results of modern science. 


Monism as a Connecting Link between Religion and Science 
The Cultur-KampfThe Relations of Church and State 
Principles of the Monistic Religion Its Three-fold Ideal : the 
Good, the True, and the Beautiful Contradiction between 
Scientific and Christian Truth Harmony of the Monistic 
and the Christian Idea of Virtue Opposition between Monistic 
and Christian Views of Art Modern Expansion and Enrich- 
ment of Our Idea of the World Landscape-Painting and the 
Modern Enjoyment of Nature The Beauties of Nature This 
World and Beyond Monistic Churches 

l\/\ ANY distinguished scientists and philosophers of 
the day, who share our monistic views, consider 
that religion is generally played out. Their mean- 
ing is that the clear insight into the evolution of the 
world which the great scientific progress of the nine- 
teenth century has afforded us will satisfy, not only, 
the causal feeling of our reason, but even our highest 
emotional cravings. This view is correct in the sense 
that the two ideas, religion and science, would indeed 
blend into one if we had a perfectly clear and consec- , 
utive system of monism. However, there are but a 
few resolute thinkers who attain to this most pure and 
lofty conception of Spinoza and Goethe. Most of the 
educated people of our time (as distinct from the un- 
cultured masses) remain in the conviction that religion 

33 i 


is a separate branch of our mental life, independent of 
science, and not less valuable and indispensable. 

If we adopt this view, we can find a means of reconcil- 
ing the two great and apparently quite distinct branch- 
es in the idea I put forward in "Monism, as a Con- 
necting-Link between Religion and Science," in 1892. 
In the preface to this Confession of Faith of a Man of 
Science I expressed myself in the following words with 
regard to its double object : " In the first place, I must 
give expression to the rational system which is logi- 
cally forced upon us by the recent progress of science ; 
it dwells in the intimate thoughts of nearly every im- 
partial and thoughtful scientist, though few have the 
courage or the disposition to avow it. In the second 
place, I would make of it a connecting-link between re- 
ligion and science, and thus do away with the antith- 
esis which has been needlessly maintained between 
these two branches of the highest activity of the hu- 
man mind. The ethical craving of our emotion is sat- 
isfied by monism no less than the logical demand for 
causality on the part of reason." 

The remarkable interest which the discourse en- 
kindled is a proof that in this monistic profession of 
faith I expressed the feeling not only of many scientists, 
but of a large number of cultured men and women of 
very different circles. Not only was I rewarded by 
hundreds of sympathetic letters, but by a wide circu- 
lation of the printed address, of which six editions 
were required within six months. I had the more rea- 
son to be content with this unexpected success, as this 
" confession of faith " was originally merely an occa- 
sional speech which I delivered unprepared on October 
9, 1892, at Altenburg, during the jubilee of the Scien- 
tific Society of East Germany. Naturally there was 



the usual demonstration on the other side ; I was fierce- 
ly attacked, not only by the ultramontane press, the 
sworn defenders of superstition, but also by the " lib- 
eral " controversialists of evangelical Christianity, 
who profess to defend both scientific truth and purified 
faith. In the seven years that have ensued since that 
time the great struggle between modern science and 
orthodox Christianity has become more threatening; 
it has grown more dangerous for science in propor- 
tion as Christianity has found support in an increasing 
mental and political reaction. In some countries the 
Church has made such progress that the freedom of 
thought and conscience, which is guaranteed by the 
laws, is in practice gravely menaced (for instance, 
in Bavaria). The great historic struggle which Dra- 
per has so admirably depicted in his Conflict between 
Religion and Science is to-day more acute and signifi- 
cant than ever. For the last twenty-seven years it has 
been rightly called the " cultur-kamp] " 

The famous encyclica and syllabus which the mili- 
tant pope, Pius IX., sent out into the entire world in 
1864 were a declaration of war on the whole of modern 
science; they demanded the blind submission of rea- 
son to the dogmas of the infallible pope. The enor- 
mity of this crude assault on the highest treasures of 
civilization even roused many indolent minds from 
the slumber of belief. Together with the subsequent 
promulgation of the papal infallibility (1870), the en- 
cyclica provoked a deep wave of irritation and an en- 
ergetic repulse which held out high hopes. In the 
new German empire, which had attained its indis- 
pensable national unity by the heavy sacrifices of the 
wars of 1866 and 1871, the insolent attacks of the pope 
were felt to be particularly offensive. On the one hand 



Germany is the cradle of the Reformation and the mod- 
ern emancipation of reason ; on the other hand, it un- 
fortunately has in its 18,000,000 Catholics a vast host 
of militant believers, who are unsurpassed by any other 
civilized people in blind obedience to their chief shep- 

The dangers of such a situation were clearly recog- 
nized by the great statesman who had solved the po- 
litical " world-riddle " of the dismemberment of Ger- 
many, and had led us by a marvellous statecraft to 
the long-desired goal of national unity and power. 
Prince Bismarck began the famous struggle with the 
Vatican, which is known as the cultur-kampf, in 1872, 
and it was conducted with equal ability and energy by 
the distinguished Minister of Worship, Falk, author 
of the May laws of 1873. Unfortunately, Bismarck 
had to desist six years afterwards. Although the great 
statesman was a remarkable judge of men and a real- 
istic politician of immense tact, he had underestimated 
the force of three powerful obstacles first, the un- 
surpassed cunning and unscrupulous treachery of the 
Roman curia ; secondly, the correlative ingratitude 
and credulity of the uneducated Catholic masses, on 
which the papacy built; and, thirdly, the power of 
apathy, the continuance of the irrational, simply be- 
cause it is in possession. Hence, in 1878, when the 
abler Leo XIII. had ascended the pontifical throne, 
the fatal " To Canossa " was heard once more. From 
that time the newly established power of Rome grew 
in strength ; partly through the unscrupulous intrigues 
and serpentine bends of its slippery Jesuitical politics, 
partly through the false Church-politics of the German 
government and the marvellous political incompetence 
of the German people. We have, therefore, at the close 



of the nineteenth century to endure the pitiful spectacle 
of the Catholic "Centre" being the most important sec- 
tion of the Reichstag, and the fate of our humiliated 
country depending on a papal party, which does not 
constitute numerically a third part of the nation. 

When the cultur-kampf began in 1872, it was justly 
acclaimed by all independent thinkers as a political 
renewal of the Reformation, a vigorous attempt to free 
modern civilization from the yoke of papal despotism. 
The whole of the Liberal press hailed Bismarck as a 
" political Luther " as the great hero, not only of the 
national unity, but also of the rational emancipation 
of Germany. Ten years afterwards, when the papacy 
had proved victorious, the same " Liberal press " changed 
its colors, and denounced the cultur-kampf as a great 
mistake; and it does the same thing to-day. The 
facts show how short is the memory of our journalists, 
how defective their knowledge of history, and how poor 
their philosophic education. The so-called " Peace be- 
tween Church and State " is never more than a suspen- 
sion of hostilities. The modern papacy, true to the des- 
potic principles it has followed for the last sixteen hun- 
dred years, is determined to wield sole dominion over the 
credulous souls of men; it must demand the absolute 
submission of the cultured State, which, as such, de- 
fends the rights of reason and science. True and en- 
during peace there cannot be until one of the comba- 
tants lies powerless on the ground. Either the Church 
wins, and then farewell to all " free science and free 
teaching " then are our universities no better than 
jails, and our colleges become cloistral schools; or 
else the modern rational State proves victorious then, 
in the twentieth century, human culture, freedom, and 
prosperity will continue their progressive development 



until they far surpass even the height of the nineteenth 

In order to compass these high aims, it is of the first 
importance that modern science not only shatter the 
false structures of superstition and sweep their ruins 
from the path, but that it also erect a new abode for 
human emotion on the ground it has cleared a " palace 
of reason," in which, under the influence of our new 
monistic views, we do reverence to the real trinity of 
the nineteenth century the trinity of " the true, the 
good, and the beautiful." In order to give a tangible 
shape to the cult of this divine ideal, we must first of 
all compare our position with the dominant forms of 
Christianity, and realize the changes that are involved 
in the substitution of the one for the other. For, in 
spite of its errors and defects, the Christian religion 
(in its primitive and purer form) has so high an ethi- 
cal value, and has entered so deeply into the most im- 
portant social and political movements of civilized his- 
tory for the last fifteen hundred years, that we must 
appeal as much as possible to its existing institutions 
in the establishment of our monistic religion. We do 
not seek a mighty revolution, but a rational reforma- 
tion, of our religious life. And just as, two thousand 
years ago, the classic poetry of the ancient Greeks 
incarnated their ideals of virtue in divine shapes, so 
may we, too, lend the character of noble goddesses to 
our three rational ideals. We must inquire into the 
features of the three goddesses of the monist truth, 
beauty, and virtue ; and we must study their relation 
to the three corresponding ideals of Christianity which 
they are to replace. 

I. The preceding inquiries (especially those of the 
first and third sections) have convinced us that truth 



unadulterated is only to be found in the temple of the 
study of nature, and that the only available paths to 
it are critical observation and reflection the empirical 
investigation of facts and the rational study of their 
efficient causes. In this way we arrive, by means of 
pure reason, at true science, the highest treasure of 
civilized man. We must, in accordance with the argu- 
ments of our sixteenth chapter, reject what is called 
" revelation," the poetry of faith, that affirms the dis- 
covery of truth in a supernatural fashion, without the 
assistance of reason. And since the entire structure 
of the Judaeo-Christian religion, like that of the Mo- 
hammedan and the Buddhistic, rests on these so-called 
revelations, and these mystic fruits of the imagination 
directly contradict the clear results of empirical re- 
search, it is obvious that we shall only attain to a 
knowledge of the truth by the rational activity of gen- 
uine science, not by the poetic imagining of a mystic 
faith. In this respect it is quite certain that the Chris- 
tian system must give way to the monistic. The god- 
dess of truth dwells in the temple of nature, in the green 
woods, on the blue sea, and on the snowy summits of 
the hills not in the gloom of the cloister, nor in the nar- 
now prisons of our jail-like schools, nor in the clouds 
of incense of the Christian churches. The paths which 
lead to the noble divinity of truth and knowledge are 
the loving study of nature and its laws, the observa- 
tion of the infinitely great star-world with the aid of 
the telescope, and the infinitely tiny cell-world with the 
aid of the microscope not senseless ceremonies and 
unthinking prayers, not alms and Peter's Pence. The 
rich gifts which the goddess of truth bestows on us are 
the noble fruits of the tree of knowledge and the ines- 
timable treasure of a clear, unified view of the world 



not belief in supernatural miracles and the illusion of 
an eternal life. 

II. It is otherwise with the divine ideal of eternal 
goodness. In our search for the truth we have entirely 
to exclude the " revelation " of the churches, and de- 
vote ourselves solely to the study of nature ; but, on the 
other hand, the idea of the good, which we call virtue, 
in our monistic religion coincides for the most part 
with the Christian idea of virtue. We are speaking, 
naturally, of the primitive and pure Christianity of the 
first three centuries, as far as we learn its moral teach- 
ing from the gospels and the epistles of Paul; it does 
not apply to the Vatican caricature of that pure doc- 
trine which has dominated European civilization, to its 
infinite prejudice, for twelve hundred years. The best 
part of Christian morality, to which we firmly adhere, 
is represented by the humanist precepts of charity and 
toleration, compassion and assistance. However, these 
noble commands, which are set down as " Christian " 
morality (in its best sense), are by no means original 
discoveries of Christianity ; they are derived from earlier 
religions. The Golden Rule, which sums up these pre- 
cepts in one sentence, is centuries older than Chris- 
tianity. In the conduct of life this law of natural mo- 
rality has been followed just as frequently by non-Chris- 
tians and atheists as it has been neglected by pious 
believers. Moreover, Christian ethics was marred by 
the great defect of a narrow insistence on altruism and 
a denunciation of egoism. Our monistic ethics lays 
equal emphasis on the two, and finds perfect virtue in 
the just balance of love of self and love of one's neigh- 
bor (cf. chap. xix.). 

III. But monism enters into its strongest opposi- 
tion to Christianity on the question of beauty. Primi- 



live Christianity preached the worthlessness of earthly 
life, regarding it merely as a preparation for an eter- 
nal life beyond. Hence it immediately followed that 
all we find in the life of man here below, all that is beau- 
tiful in art and science, in public and in private life, 
is of no real value. The true Christian must avert 
his eyes from them; he must think only of a worthy 
preparation for the life beyond. Contempt of nature, 
aversion from all its inexhaustible charms, rejection 
of every kind of fine art, are Christian duties; and 
they are carried out to perfection when a man sepa- 
rates himself from his fellows, chastises his body, and 
spends all his time in prayer in the cloister or the her- 
mit's cell. 

History teaches us that this ascetical morality that 
would scorn the whole of nature had, as a natural con- 
sequence, the very opposite effect to that it intended. 
Monasteries, the homes of chastity and discipline, 
soon became dens of the wildest orgies; the sexual 
commerce of monks and nuns has inspired shoals of 
novels, as it is so faithfully depicted in the literature 
of the Renaissance. The cult of the " beautiful," which 
was then practised, was in flagrant contradiction with 
the vaunted "abandonment of the world"; and the 
same must be said of the pomp and luxury which soon 
developed in the immoral private lives of the higher 
ecclesiastics and in the artistic decoration of Christian 
churches and monasteries. 

It may be objected that our view is refuted by the 
splendor of Christian art, which, especially in the best 
days of the Middle Ages, created works of undying 
beauty. The graceful Gothic cathedrals and Byzan- 
tine basilicas, the hundreds of magnificent chapels, 
the thousands of marble statues of saints and martyrs, 



the millions of fine pictures of saints, of profoundly 
conceived representations of Christ and the madonna 
all are proofs of the development of a noble art in the 
Middle Ages, which is unique of its kind. All these 
splendid monuments of mediaeval art are untouched 
in their high aesthetic value, whatever we say of their 
mixture of truth and fancy. Yes; but what has all 
that to do with the pure teaching of Christianity with 
that religion of sacrifice that turned scornfully away 
from all earthly parade and glamour, from all material 
beauty and art ; that made light of the life of the fam- 
ily and the love of woman ; that urged an exclusive con- 
cern as to the immaterial goods of eternal life? The 
idea of a Christian art is a contradiction in terms a 
contradictio in adjecto. The wealthy princes of the 
Church who fostered it were candidly aiming at very 
different ideals, and they completely attained them. 
In directing the whole interest and activity of the hu- 
man mind in the Middle Ages to the Christian Church 
and its distinctive art they were diverting it from nature 
and from the knowledge of the treasures that were hid- 
den in it, and would have conducted to independent 
science. Moreover, the daily sight of the huge images 
of the saints and of the scenes of " sacred history " con- 
tinually reminded the faithful of the vast collection 
of myths that the Church had made. The legends 
themselves were taught and believed to be true nar- 
ratives, and the stories of miracles to be records of act- 
ual events. It cannot be doubted that in this respect 
Christian art has exercised an immense influence on 
general culture, and especially in the strengthening 
of Christian belief an influence which still endures 
throughout the entire civilized world. 

The diametrical opposite of this dominant Christian 


art is the new artistic tendency which has been devel- 
oped during the present century in connection with 
science. The remarkable expansion of our knowl- 
edge of nature, and the discovery of countless beauti- 
ful forms of life, which it includes, have awakened quite 
a new aesthetic sense in our generation, and thus given 
a new tone to painting and sculpture. Numerous sci- 
entific voyages and expeditions for the exploration 
of unknown lands and seas, partly in earlier centuries, 
but more especially in the nineteenth, have brought to 
light an undreamed abundance of new organic forms. 
The number of new species of animals and plants soon 
became enormous, and among them (especially among 
the lower groups that had been neglected before) there 
were thousands of forms of great beauty and interest, 
affording an entirely new inspiration for painting, sculp- 
ture, architecture, and technical art. In this respect a 
new world was revealed by the great advance of mi- 
croscopic research in the second half of the century, and 
especially by the discovery of the marvellous inhabi- 
tants of the deep sea, which were first brought to light 
by the famous expedition of the Challenger (1872-76). 
Thousands of graceful radiolaria and thalamophora, 
of pretty medusae and corals, of extraordinary mol- 
luscs, and crabs, suddenly introduced us to a wealth 
of hidden organisms beyond all anticipation, the pe- 
culiar beauty and diversity of which far transcend all 
the creations of the human imagination. In the fifty 
large volumes of the account of the Challenger expe- 
dition a vast number of these beautiful forms are 
delineated on three thousand plates; and there are 
millions of other lovely organisms described in other 
great works that are included in the fast-growing liter- 
ature of zoology and botany of the last ten years. I 



began on a small scale to select a number of these 
beautiful forms for more popular description in my 
Art Forms in Nature (1899). 

However, there is now no need for long voyages and 
costly works to appreciate the beauties of this world. 
A man needs only to keep his eyes open and his mind 
disciplined. Surrounding nature offers us everywhere 
a marvellous wealth of lovely and interesting objects 
of all kinds. In every bit of moss and blade of grass, 
in every beetle and butterfly, we find, when we exam- 
ine it carefully, beauties which are usually overlooked. 
Above all, when we examine them with a powerful glass 
or, better still, with a good microscope, we find every- 
where in nature a new world of inexhaustible charms. 

But the nineteenth century has not only opened our 
eyes to the aesthetic enjoyment of the microscopic world ; 
it has shown us the beauty of the greater objects in 
nature. Even at its commencement it was the fashion 
to regard the mountains as magnificent but forbidding, 
and the sea as sublime but dreaded. At its close the 
majority of educated people especially they who dwell 
in the great cities are delighted to enjoy the glories 
of the Alps and the crystal splendor of the glacier world 
for a fortnight every year, or to drink in the majesty of 
the ocean and the lovely scenery of its coasts. All these 
sources of the keenest enjoyment of nature have only 
recently been revealed to us in all their splendor, and 
the remarkable progress we have made in facility and 
rapidity of conveyance has given even the less wealthy 
an opportunity of approaching them. All this progress 
in the aesthetic enjoyment of nature and, proportion- 
ately, in the scientific understanding of nature implies 
an equal advance in higher mental development and, 
consequently, in the direction of our monistic religion. 



The opposite character of our naturalistic century to 
that of the anthropistic centuries that preceded is es- 
pecially noticeable in the different appreciation and 
spread of illustrations of the most diverse natural ob- 
jects. In our own days a lively interest in artistic 
work of that kind has been developed, which did not 
exist in earlier ages ; it has been supported by the re- 
markable progress of commerce and technical art which 
have facilitated a wide popularization of such illustra- 
tions. Countless illustrated periodicals convey along 
with their general information a sense of the inexhaust- 
ible beauty of nature in all its departments. In par- 
ticular, landscape-painting has acquired an importance 
that surpassed all imagination. In the first half of the 
century one of our greatest and most erudite scientists, 
Alexander Humboldt, had pointed out that the devel- 
opment of modern landscape -painting is not only of 
great importance as an incentive to the study of nature 
and as a means of geographical description, but that 
it is to be commended in other respects as a noble edu- 
cative medium. Since that time the taste for it has 
considerably increased. It should be the aim at every 
school to teach the children to enjoy scenery at an early 
age, and to give them the valuable art of imprinting 
on the memory by a drawing or water-color sketch. 

The infinite wealth of nature in what is beautiful 
and sublime offers every man with open eyes and an 
aesthetic sense an incalculable sum of choicest gifts. 
Still, however valuable and agreeable is the immediate 
enjoyment of each single gift, its worth is doubled by a 
knowledge of its meaning and its connection with the 
rest of nature. When Humboldt gave us the " outline 
of a physical description of the world " in his magnifi- 
cent Cosmos forty years ago, and when he combined 



scientific and aesthetic consideration so happily in his 
standard Prospects of Nature, he justly indicated how 
closely the higher enjoyment of nature is connected 
with the " scientific establishment of cosmic laws/' and 
that the conjunction of the two serves to raise human 
nature to a higher stage of perfection. The astonish- 
ment with which we gaze upon the starry heavens and 
the microscopic life in a drop of water, the awe with 
which we trace the marvellous working of energy in 
the motion of matter, the reverence with which we 
grasp the universal dominance of the law of substance 
throughout the universe all these are part of our 
emotional life, falling under the heading of " natural 

This progress of modern times in knowledge of the 
true and enjoyment of the beautiful expresses, on the 
one hand, a valuable element of our monistic religion, 
but is, on the other hand, in fatal opposition to Chris- 
tianity. For the human mind is thus made to live on 
this side of the grave ; Christianity w r ould have it ever 
gaze beyond. Monism teaches that we are perishable 
children of the earth, who for one or two, or, at the 
most, three generations, have the good fortune to enjoy 
the treasures of our planet, to drink of the inexhausti- 
ble fountain of its beauty, and to trace out the marvel- 
lous play of its forces. Christianity would teach us 
that the earth is "a vale of tears/' in which we have 
but a brief period to chasten and torment ourselves in 
order to merit the life of eternal bliss beyond. Where 
this " beyond " is, and of what joys the glory of this 
eternal life is compacted, no revelation has ever told 
us. As long as " heaven " was thought to be the blue 
vault that hovers over the disk of our planet, and is il- 
lumined by the twinkling light of a few thousand stars, 



the human imagination could picture to itself the am- 
brosial banquets of the Olympic gods above or the laden 
tables of the happy dwellers in Valhalla. But now all 
these deities and the immortal souls that sat at their 
tables are " houseless and homeless/' as David Strauss 
has so ably described ; for we know from astrophysical 
science that the immeasurable depths of space are filled 
with a prosaic ether, and that millions of heavenly 
bodies, ruled by eternal laws of iron, rush hither and 
thither in the great ocean, in their eternal rhythm of 
life and death. 

The places of devotion, in which men seek the 
satisfaction of their religious emotions and worship 
the objects of their reverence, are regarded as sacred 
" churches." The pagodas of Buddhistic Asia, the 
Greek temples of classical antiquity, the synagogues 
of Palestine, the mosques of Egypt, the Catholic cathe- 
drals of the south, and the Protestant cathedrals of the 
north, of Europe all these " houses of God " serve to 
raise man above the misery and the prose of daily life, 
to lift him into the sacred, poetic atmosphere of a high- 
er, ideal world. They attain this end in a thousand 
different ways, according to their various forms of wor- 
ship and their age. The modern man who " has sci- 
ence and art " and, therefore, " religion " needs no 
special church, no narrow, enclosed portion of space. 
For through the length and breadth of free nature, 
wherever he turns his gaze, to the whole universe or 
to any single part of it, he finds, indeed, the grim " strug- 
gle for life," but by its side are ever " the good, the true, 
and the beautiful " ; his church is commensurate with 
the whole of glorious nature. Still, there will always 
be men of special temperament who will desire to have 
decorated temples or churches as places of devotion 



to which they may withdraw. Just as the Catholics 
had to relinquish a number of churches to the Reforma- 
tion in the sixteenth century, so a still larger number 
will pass over to " free societies " of monists in the com- 
ing years. 


Monistic and Dualistic Ethics Contradiction of Pure and Prac. 
tical Reason in Kant His Categorical Imperative The Neo> 
Kantians Herbert Spencer Egoism and Altruism Equiv- 
alence of the Two Instincts The Fundamental Law of Ethics : 
the Golden Rule Its Antiquity Christian Ethics Contempt 
of Self, the Body, Nature, Civilization, the Family, Woman 
Roman Catholic Ethics Immoral Results of Celibacy Ne- 
cessity for the Abolition of the Law of Celibacy, Oral Confes- 
sion, and Indulgences State and Church Religion a Private 
Concern Church and School State and School Need of 
School Reform 

T^HE practical conduct of life makes a number of 
definite ethical claims on a man which can only 
be duly and naturally satisfied when they are in com- 
plete harmony with his view of the world. In accord- 
ance with this fundamental principle of our monistic 
philosophy, our whole system of ethics must be ration- 
ally connected with the unified conception of the cos- 
mos which we have formed by our advanced knowl- 
edge of the laws of nature. Just as the infinite uni- 
verse is one great whole in the light of our monistic 
teaching, so the spiritual and moral life of man is a part 
of this cosmos, and our naturalistic ordering of it must 
also be monistic. There are not two different, separate 
worlds the one physical and material, and the other 
moral and immaterial. 



The great majority of philosophers and theologians 
still hold the contrary opinion. They affirm, with 
Kant, that the moral world is quite independent of 
the physical, and is subject to very different laws ; hence 
a man's conscience, as the basis of his moral life, must 
also be quite independent of our scientific knowledge 
of the world, and must be based rather on his religious 
faith. On that theory the study of the moral world 
belongs to practical reason, while that of nature, or of 
the physical world, is referred to pure or theoretical 
reason. This unequivocal and conscious dualism of 
Kant's philosophy was its greatest defect ; it has caused, 
and still causes, incalculable mischief. First of all 
the " critical Kant " had built up the splendid and mar- 
vellous palace of pure reason, and convincingly proved 
that the three great central dogmas of metaphysics 
a personal God, free will, and the immortal soul had 
no place whatever in it, and that no rational proof could 
be found of their reality. Afterwards, however, the 
"dogmatic Kant" superimposed on this true crystal 
palace of pure reason the glittering, ideal castle in the 
air of practical reason, in which three imposing church- 
naves were designed for the accommodation of those 
three great mystic divinities. When they had been 
put out at the front door by rational knowledge they 
returned by the back door under the guidance of 
irrational faith. 

The cupola of his great cathedral of faith was crowned 
by Kant with his curious idol, the famous " categorical 
imperative." According to it, the demand of the uni- 
versal moral law is unconditional, independent of any 
regard to actuality or potentiality. It runs : " Act at 
all times in such wise that the maxim (or the subjective 
kw of thy will) may hold good as a principle of a uni- 



versal law. " On that theory all normal men would have 
the same sense of duty. Modern anthropology has 
ruthlessly dissipated that pretty dream ; it has shown 
that conceptions of duty differ even more among un- 
civilized than among civilized nations. All the actions 
and customs which we regard as sins or loathsome 
crimes (theft, fraud, murder, adultery, etc.) are con- 
sidered by other nations in certain circumstances to 
be virtues, or even sacred duties. 

Although the obvious contradiction of the two forms 
of reason in Kant's teaching, the fundamental antag- 
onism of pure and practical reason, was recognized 
and attacked at the very beginning of the century, it 
is still pretty widely accepted. The modern school 
of neo-Kantians urges a " return to Kant " so press- 
ingly precisely on account of this agreeable dualism; 
the Church militant zealously supports it because it 
fits in admirably with its own mystic faith. But it 
met with an effective reverse at the hands of modern 
science in the second half of the nineteenth century, 
which entirely demolished the theses of the system of 
practical reason. Monistic cosmology proved, on the 
basis of the law of substance, that there is no person- 
al God; comparative and genetic psychology showed 
that there cannot be an immortal soul ; and monistic 
physiology proved the futility of the assumption of 
" free will." Finally, the science of evolution made 
it clear that the same eternal iron laws that rule in the 
inorganic world are valid too in the organic and moral 

But modern science gives not only a negative sup- 
port to practical philosophy and ethics in demolishing 
the Kantian dualism, but it renders the positive service 
of substituting for it the new structure of ethical mon- 
** 349 


ism. It shows that the feeling of duty does not rest 
on an illusory " categorical imperative," but on the 
solid ground of social instinct, as we find in the case 
of all social animals. It regards as the highest aim of 
all morality the re-establishment of a sound harmony 
between egoism and altruism, between self-love and 
the love of one's neighbor. It is to the great English 
philosopher, Herbert Spencer, that we owe the found- 
ing of this monistic ethics on a basis of evolution. 

Man belongs to the social vertebrates, and has, there- 
fore, like all social animals, two sets of duties first 
to himself, and secondly to the society to which he be- 
longs. The former are the behests of self-love or ego- 
ism, the latter of love for one's fellows or altruism. The 
two sets of precepts are equally just, equally natural, 
and equally indispensable. If a man desire to have 
the advantage of living in an organized community, 
he has to consult not only his own fortune, but also 
that of the society, and of the " neighbors " who form 
the society. He must realize that its prosperity is his 
own prosperity, and that it cannot suffer without his 
own injury. This fundamental law of society is so 
simple and so inevitable that one cannot understand 
how it can be contradicted in theory or in practice ; yet 
that is done to-day, and has been done for thousands 
of years. 

The equal appreciation of these two natural impulses, 
or the moral equivalence of self-love and love of others, 
is the chief and the fundamental principle of our mo- 
rality. Hence the highest aim of all ethics is very 
simple it is the re-establishment of " the natural equal- 
ity of egoism and altruism, of the love of one's self and 
the love of one's neighbor." The Golden Rule says: 
" Do unto others as you would that they should do unto 



you." From this highest precept of Christianity it 
follows of itself that we have just as sacred duties tow- 
ards ourselves as we have towards our fellows. I have 
explained my conception of this principle in my Mon- 
ism, and laid down three important theses, (i) Both 
these concurrent impulses are natural laws, of equal 
importance and necessity for the preservation of the 
family and the society; egoism secures the self-pres- 
ervation of the individual, altruism that of the species 
which is made up of the chain of perishable individ- 
uals. (2) The social duties which are imposed by the 
social structure of the associated individuals, and by 
means of w r hich it secures its preservation, are merely 
higher evolutionary stages of the social instincts, which 
we find in all higher social animals (as " habits which 
have become hereditary "). (3) In the case of civilized 
man all ethics, theoretical or practical, being "a sci- 
ence of rules/' is connected with his view of the world 
at large, and consequently with his religion. 

From the recognition of the fundamental principle 
of our morality we may immediately deduce its high- 
est precept, that noble command, which is often called 
the Golden Rule of morals, or, briefly, the Golden Rule. 
Christ repeatedly expressed it in the simple phrase: 
"Thou shalt love thy neighbor as thyself." Mark 
adds that " there is no greater commandment than this," 
and Matthew says: "In these two commandments 
is the whole law and the prophets." In this greatest 
and highest commandment our monistic ethics is com- 
pletely at one with Christianity. We must, however, 
recall the historical fact that the formulation of this 
supreme command is not an original merit of Christ, 
as the majority of Christian theologians affirm and 
their uncritical supporters blindly accept. The Gold- 


en Rule is five hundred years older than Christ; it 
was laid down as the highest moral principle by many 
Greek and Oriental sages. Pittacus, of Mylene, one 
of the seven wise men of Greece, said six hundred and 
twenty years before Christ : " Do not that to thy neigh- 
bor that thou wouldst not suffer from him." Confu- 
cius, the great Chinese philosopher and religious found- 
er (who rejected the idea of a personal God and of the 
immortality of the soul), said five hundred years B.C. : 
" Do to every man as thou wouldst have him do to thee ; 
and do not to another what thou wouldst not have him 
do to thee. This precept only dost thou need; it is 
the foundation of all other commandments." Aristotle 
taught about the middle of the fourth century B.C. : 
u We must act towards others as we wish others to act 
towards us." In the same sense, and partly in the 
same words, the Golden Rule was given by Thales, 
Isocrates, Aristippus, Sextus, the Pythagorean, and 
other philosophers of classic antiquity several cen- 
turies before Christ. From this collection it is clear 
that the Golden Rule had a polyphyletic origin that 
is, it was formulated by a number of philosophers at 
different times and in different places, quite indepen- 
dently of each other. Otherwise it must be assumed 
that Jesus derived it from some other Oriental source, 
from ancient Semitic, Indian, Chinese, or especially 
Buddhistic traditions, as has been proved in the case 
of most of the other Christian doctrines. 

As the great ethical principle is thus twenty-five hun- 
dred years old, and as Christianity itself has put it at 
the head of its moral teaching as the highest and all- 
embracing commandment, it follows that our monistic 
ethics is in complete harmony on this important point, 
not only with the ethics of the ancient heathens, but also 

35 2 


with that of Christianity. Unfortunately this harmony 
is disturbed by the fact that the gospels and the Paul 
me epistles contain many other points of moral teach- 
ing, which contradict our first and supreme command- 
ment. Christian theologians have fruitlessly striven 
to explain away these striking and painful contradic- 
tions by their ingenious interpretations. We need not 
enter into that question now, but we must briefly con- 
sider those unfortunate aspects of Christian ethics 
which are incompatible with the better thought of the 
modern age, and which are distinctly injurious in their 
practical consequences. Of that character is the con- 
tempt which Christianity has shown for self, for the 
body, for nature, for civilization, for the family, and 
for woman. 

I. The supreme mistake of Christian ethics, and 
one which runs directly counter to the Golden Rule, 
is its exaggeration of love of one's neighbor at the ex- 
pense of self-love. Christianity attacks and despises 
egoism on principle. Yet that natural impulse is ab- 
solutely indispensable in view of self-preservation; 
indeed, one may say that even altruism, its apparent 
opposite, is only an enlightened egoism. Nothing 
great or elevated has ever taken place without egoism, 
and without the passion that urges us to great sacri- 
fices. It is only the excesses of the impulse that are 
injurious. One of the Christian precepts that were 
impressed upon us in our early youth as of great impor- 
tance, and that are glorified in millions of sermons, is : 
" Love your enemies, bless them that curse you, do 
good to them that hate you, and pray for them which 
despitefully use you and persecute you." It is a very 
ideal precept, but as useless in practice as it is unnat- 
ural. So it is with the counsel, " If any man will take 



away thy coat, let him have thy cloak also." Trans- 
lated into the terms of modern life, that means : " When 
some unscrupulous scoundrel has defrauded thee of 
half thy goods, let him have the other half also." Or, 
again, in the language of modern politics: "When 
the pious English take from you simple Germans one 
after another of your new and valuable colonies in 
Africa, let them have all the rest of your colonies also 
or, best of all, give them Germany itself." And, 
while we touch on the marvellous world-politics of 
modern England, we may note in passing its direct 
contradiction of every precept of Christian charity, 
which is more frequently on the lips of that great nation 
than of any other nation in the world. However, the 
glaring contradiction between the theoretical, ideal, 
altruistic morality of the human individual and the 
real, purely selfish morality of the human community, 
and especially of the civilized Christian state, is a fa- 
miliar fact. It would be interesting to determine math- 
ematically in what proportion among organized men 
the altruistic ethical ideal of the individual changes 
into its contrary, the purely egoistic "real politics" 
of the state and the nation. 

II. Since the Christian faith takes a wholly dualis- 
tic view of the human organism and attributes to the 
immortal soul only a temporary sojourn in the mortal 
frame, it very naturally sets a much greater value on 
the soul than on the body. Hence results that neglect 
of the care of the body, of training, and of cleanliness 
which contrasts the life of the Christian Middle Ages 
so unfavorably with that of pagan classical antiquity. 
Christian ethics contains none of those firm commands 
as to daily ablutions which are theoretically laid down 
and practically fulfilled in the Mohammedan, Hindoo, 



and other religions. In many monasteries the ideal of 
the pious Christian is the man who does not wash and 
clothe himself properly, who never changes his malo- 
dorous gown, and who, instead of regular work, fills 
up his useless life with mechanical prayers, senseless 
fasts, and so forth. As a special outgrowth of this 
contempt of the body we have the disgusting discipline 
of the flagellants and other ascetics. 

III. One source of countless theoretical errors and 
practical blemishes, of deplorable crudity and privation, 
is found in the false anthropism of Christianity that 
is, in the unique position which it gives to man, as the 
image of God, in opposition to all the rest of nature. In 
this way it has contributed, not only to an extremely 
injurious isolation from our glorious mother " nature/' 
but also to a regrettable contempt of all other organ- 
isms. Christianity has no place for that well-known 
love of animals, that sympathy with the nearly related 
and friendly mammals (dogs, horses, cattle, etc.), 
which is urged in the ethical teaching of many of the 
older religions, especially Buddhism. Whoever has 
spent much time in the south of Europe must have 
often witnessed those frightful sufferings of animals 
which fill us friends of animals with the deepest sym- 
pathy and indignation. And when one expostulates 
with these brutal " Christians " on their cruelty, the 
only answer is, with a laugh : " But the beasts are not 
Christians." Unfortunately Descartes gave some sup- 
port to the error in teaching that man only has a sen- 
sitive soul, not the animal. 

How much more elevated is our monistic ethics than 
the Christian in this regard! Darwinism teaches us 
that we have descended immediately from the primates, 
and, in a secondary degree, from a long series of earlier 



mammals, and that, therefore, they are " our brothers " ; 
physiology informs us that they have the same nerves 
and sense-organs as we, and the same feelings of pleas- 
ure and pain. No sympathetic monistic scientist 
would ever be guilty of that brutal treatment of ani- 
mals which comes so lightly to the Christian in his 
anthropistic illusion to the " child of the God of love." 
Moreover, this Christian contempt of nature on prin- 
ciple deprives man of an abundance of the highest 
earthly joys, especially of the keen, ennobling enjoy- 
ment of nature. 

IV. Since, according to Christ's teaching, our planet 
is " a vale of tears," and our earthly life is valueless 
and a mere preparation for a better life to come, it has 
succeeded in inducing men to sacrifice all happiness 
on this side of eternity and make light of all earthly 
goods. Among these " earthly goods," in the case of 
the modern civilized man, we must include the count- 
less great and small conveniences of technical science, 
hygiene, commerce, etc., which have made modern life 
cheerful and comfortable ; we must include all the grati- 
fications of painting, sculpture, music, and poetry, 
which flourished exceedingly even during the Middle 
Ages (in spite of its principles), and which we esteem 
as " ideal pleasures " ; we must include all that invalu- 
able progress of science, especially the study of nature, 
of which the nineteenth century is justly proud. All 
these " earthly goods," that have so high a value in the 
eyes of the monist, are worthless nay, injurious for 
the most part, according to Christian teaching ; the 
stern code of Christian morals should look just as un- 
favorably on the pursuit of these pleasures as our hu- 
manistic ethics fosters and encourages it. Once more, 
therefore, Christianity is found to be an enemy to civili- 



zation, and the struggle which modern thought and 
science are compelled to conduct with it is, in this addi- 
tional sense, a " cultur-kampf ." 

V. Another of the most deplorable aspects of Chris- 
tian morality is its belittlement of the life of the family, 
of that natural living together with our next of kin 
which is just as necessary in the case of man as in the 
case of all the higher social animals. The family is 
justly regarded as the " foundation of society/' and the 
healthy life of the family is a necessary condition of 
the prosperity of the State. Christ, however, was of a 
very different opinion: with his gaze ever directed to 
" the beyond," he thought as lightly of woman and the 
family as of all other goods of " this life/' Of his in- 
frequent contact with his parents and sisters the gos- 
pels have very little to say ; but they are far from rep- 
resenting his relations with his mother to have been so 
tender and intimate as they are poetically depicted in 
so many thousands of pictures. He was not married 
himself. Sexual love, the first foundation of the fam- 
ily union, seems to have been regarded by Jesus as a 
necessary evil. His most enthusiastic apostle, Paul, 
went still farther in the same direction, declaring it to 
be better not to marry than to marry : * It is good for 
a man not to touch a woman." If humanity were 
to follow this excellent counsel, it would soon be rid 
of all earthly misery and suffering ; it would be killed 
off by such a " radical cure " within half a century. 

VI. As Christ never knew the love of woman, he 
had no personal acquaintance with that refining of 
man's true nature that comes only from the intimate 
life of man with woman. The intimate sexual union, 
on which the preservation of the human race depends, 
is just as important on that account as the spiritual 



penetration of the two sexes, or the mutual comple- 
ment which they bring to each other in the practical 
wants of daily life as well as in the highest ideal func- 
tions of the soul. For man and woman are two differ- 
ent organisms, equal in worth, each having its charac- 
teristic virtues and defects. As civilization advanced, 
this ideal value of sexual love was more appreciated, 
and woman held in higher honor, especially among the 
Teutonic races ; she is the inspiring source of the high- 
est achievements of art and poetry. But Christ was as 
far from this view as nearly the whole of antiquity; 
he shared the idea that prevailed everywhere in the 
East that woman is subordinate to man, and inter- 
course with her is " unclean." Long-suffering nature 
has taken a fearful revenge for this blunder; its sad 
consequences are written in letters of blood in the his- 
tory of the papal Middle Ages. 

The marvellous hierarchy of the Roman Church, that 
never disdained any means of strengthening its spirit- 
ual despotism, found an exceptionally powerful instru- 
ment in the manipulation of this " unclean " idea, and 
in the promotion of the ascetic notion that abstinence 
from intercourse with women is a virtue of itself. In the 
first few centuries after Christ a number of priests vol- 
untarily abstained from marriage, and the supposed 
value of this celibacy soon rose to such a degree that 
it was made obligator}^. In the Middle Ages the seduc- 
tion of women of good repute and of their daughters by 
Catholic priests (the confessional was an active agency 
in the business) was a public scandal ; many commu- 
nities, in order to prevent such things, pressed for a 
license of concubinage to be given to the clergy. 
And it was done in many, and sometimes very ro- 
matic, ways. Thus, for instance, the canon law that 



the priest's cook should not be less than forty years old 
was very cleverly "explained" in the sense that the 
priest might have two cooks, one in the presbytery, 
another without ; if one was twenty-four and the other 
eighteen, that made forty -two together two years 
above the prescribed age. At the Christian councils, 
at which heretics were burned alive, the cardinals and 
bishops sat down with whole troops of prostitutes. 
The private and public debauchery of the Catholic 
clergy was so scandalous and dangerous to the com- 
monwealth that there was a general rebellion against 
it before the time of Luther, and a loud demand for a 
" reformation of the church in head and members." It 
is well known that these immoral relations still con- 
tinue in Roman Catholic lands, although more in 
secret. Formerly proposals were made from time to 
time for the definitive abrogation of celibacy, as was 
done, for instance, in the chambers of Baden, Ba- 
varia, Hesse, Saxony, and other lands ; but they have, 
unfortunately, hitherto proved unavailing. In the 
German Reichstag, in which the ultramontane Centre 
is now proposing the most ridiculous measures for the 
suppression of sexual immorality, there is now no 
party that will urge the abolition of celibacy in the in- 
terest of public morality. The so-called " Freethought " 
Party and the utopian social democracy coquette with 
the favor of the Centre. 

The modern state that would lift not only the mate- 
rial, but the moral, life of its people to a higher level 
is entitled, and indeed bound, to sweep away such 
unworthy and harmful conditions. The obligatory 
celibacy of the Catholic clergy is as pernicious and 
immoral as the practice of auricular confession or 
the sale of indulgences. All three have nothing what- 



ever to do with primitive Christianity. All three are 
directly opposed to true Christian morality. All three 
are disreputable inventions of the papacy, designed 
for the sole purpose of strengthening its despotic rule 
over the credulous masses and making as much 
material profit as possible out of them. 

The Nemesis of history will sooner or later exact a 
terrible account of the Roman papacy, and the millions 
who have been robbed of their happiness by this de- 
generate religion will help to give it its death-blow in 
the coming twentieth century at least, in every truly 
civilized state. It has been recently calculated that 
the number of men who lost their lives in the papal 
persecutions of heretics, the Inquisition, the Christian 
religious wars, etc., is much more than ten millions. 
But what is this in comparison with the tenfold greater 
number of the unfortunate moral victims of the in- 
stitutions and the priestly domination of the degen- 
erate Christian Church with the unnumbered millions 
whose higher mental life was extinguished, whose con- 
science was tortured, whose family life was destroyed, 
by the Church? We may with truth apply the words 
of Goethe in his Bride of Corinth : 

" Victims fall, nor lambs nor bulls, 
But human victims numberless." 

In the great cultur-kampf , which must go on as long 
as these sad conditions exist, the first aim must be the 
absolute separation of Church and State. There shall 
be "a free Church in a free State" that is, every Church 
shall be free in the practice of its special worship and 
ceremonies, and in the construction of its fantastic 
poetry and superstitious dogmas with the sole con- 
dition that they contain no danger to social order or 



morality. Then there will be equal rights for all. Free 
societies and monistic religious bodies shall be equally 
tolerated, and just as free in their movements as Lib- 
eral Protestant and orthodox ultramontane congrega- 
tions. But for all these " faithful " of the most diverse 
sects religion will have to be a private concern. The 
state shall supervise them, and prevent excesses ; but 
it must neither oppress nor support them. Above all, 
the ratepayers shall not be compelled to contribute to 
the support and spread of a " faith " which they hon- 
estly believe to be a harmful superstition. In the United 
States such a complete separation of Church and State 
has been long accomplished, greatly to the satisfaction 
of all parties. They have also the equally important 
separation of the Church from the school ; that is, 
undoubtedly, a powerful element in the great advance 
which science and culture have recently made in 

It goes without saying that this exclusion of the 
Church from the school only refers to its sectarian 
principles, the particular form of belief which each 
Church has evolved in the course of its life. This sec- 
tarian education is purely a private concern, and 
should be left to parents and tutors, or to such priests or 
teachers as may have the personal confidence of the 
parents. Instead of the rejected sectarian instruction, 
two important branches of education will be introduced 
monistic or humanist ethics and comparative relig- 
ion. During the last thirty years an extensive litera- 
ture has appeared dealing with the new system of ethics 
which has been raised on the basis of modern science 
especially evolutionary science. Comparative re- 
ligion will be a natural companion to the actual ele- 
mentary instruction in " biblical history * and in the 



mythology of Greece and Rome. Both of these will 
remain in the curriculum. The reason for that is ob- 
vious enough ; the whole of our painting and sculpt- 
ure, the chief branches of monistic aesthetics, are inti- 
mately blended with the Christian, Greek, and Roman 
mythologies. There will only be this important dif- 
ference that the Christian myths and legends will 
not be taught as truths, but as poetic fancies, like the 
Greek and Roman myths ; the high value of the ethical 
and aesthetical material they contain will not be les- 
sened, but increased, by this means. As regards the 
Bible, the "book of books" will only be given to the 
children in carefully selected extracts (a sort of "school 
Bible ") ; in this way we shall avoid the besmirching 
of the child's imagination with the unclean stories 
and passages which are so numerous in the Old Tes- 

Once the modern State has freed itself and its schools 
from the fetters of the Church, it will be able to de- 
vote more attention to the improvement of education. 
The incalculable value of a good system of education 
has forced itself more and more upon us as the many 
aspects of modern civilized life have been enlarged and 
enriched in the course of the century. But the devel- 
opment of the educational methods has by no means 
kept pace with life in general. The necessity for a 
comprehensive reform of our schools is making itself 
felt more and more. On this question, too, a number 
of valuable works have appeared in the course of the 
last forty years. We shall restrict ourselves to mak- 
ing a few general observations which we think of spe- 
cial importance. 

I. In all education up to the present time man has 
played the chief part, and especially the grammatical 



study of his language ; the study of nature was entirely 

2. In the school of the future nature will be the chief 
object of the study ; a man shall learn a correct view of 
the world he lives in ; he will not be made to stand out- 
side of and opposed to nature, but be represented as its 
highest and noblest product. 

3. The study of the classical tongues (Latin and! 
Greek), which has hitherto absorbed most of the pu- 
pils'* time and energy, is indeed valuable ; but it will 
be much restricted, and confined to the mere elements 
(obligatory for Latin, optional for Greek). 

4. In consequence, modern languages must be all the 
more cultivated in all the higher schools (English and 
French to be obligatory, Italian optional). 

5. Historical instruction must pay more attention to 
the inner mental and spiritual life of a nation, and to 
the development of its civilization, and less to its ex- 
ternal history (the vicissitudes of dynasties, wars, and 
so forth). 

6. The elements of evolutionary science, must be 
learned in conjunction with cosmology, geology must 
go with geography, and anthropology with biology. 

7. The first principles of biology must be familiar to 
every educated man; the modern training in observa- 
tion furnishes an attractive introduction to the biologi- 
cal sciences (anthropology, zoology, and botany). A 
start must be made with descriptive system (in con- 
junction with aetiology or bionomy) ; the elements of 
anatomy and physiology to be added later on. 

8. The first principles of physics and chemistry must 
also be taught, and their exact establishment with the 
aid of mathematics. 

9. Every pupil must be taught to draw well, and 



from nature ; and, wherever it is possible, the use of 
water-colors. The execution of drawings and of water- 
color sketches from nature (of flowers, animals, land- 
scapes, clouds, etc.) not only excites interest in nature 
and helps memory to enjoy objects, but it gives the 
pupil his first lesson in seeing correctly and under- 
standing what he has seen. 

10. Much more care and time must be devoted than 
has been done hitherto to corporal exercise, to gymnas- 
tics and swimming ; but it is especially important to 
have walks in common every week, and journeys on 
foot during the holidays. The lesson in observation 
w^hich they obtain in this way is invaluable. 

The chief aim of higher education up to the present 
time, in most countries, has oeen a preparation for the 
subsequent profession, and the acquisition of a certain 
amount of information and direction for civic duties. 
The school of the twentieth century will have for its 
main object the formation of independent thought, the 
clear understanding of the knowledge acquired, and 
an insight into the natural connection of phenomena. 
If the modern state gives every citizen a vote, it should 
also give him the means of developing his reason by a 
proper education, in order to make a rational use of 
his vote for the commonweal. 




A Glance at the Progress of the Nineteenth Century in Solving 
Cosmic Problems I. Progress of Astronomy and Cosmology 
Physical and Chemical Unity of the Universe Cosmic 
Metamorphoses Evolution of the Planetary System Anal- 
ogy f the Phylogenetic Processes on the Earth and on 
Other Planets Organic Inhabitants of Other Heavenly Bod- 
ies Periodic Variation in the Making of Worlds II. Prog- 
ress of Geology and Palaeontology Neptunism and Vulcan- 
ism Theory of Continuity III. Progress of Physics and 
Chemistry IV. Progress of Biology Cellular Theory and 
Theory of Descent V. Anthropology Origin of Man Gen- 
eral Conclusion 

A T the close of our philosophic study of .the riddles 
** of the universe we turn with confidence to the 
answer to the momentous question, How nearly have 
we approached to a solution of them? What is the 
value of the immense progress which the passing nine- 
teenth century has made in the knowledge of nature? 
And what prospect does it open out to us for the future, 
for the further development of our system in the twen- 
tieth century, at the threshold of which we pause? 
Every unprejudiced thinker who impartially consid- 
ers the solid progress of our empirical science, and the 
unity and clearness of our philosophic interpretation 
of it, will share our view : the nineteenth century has 
made greater progress in knowledge of the world and 
25 365 


in grasp of its nature than all its predecessors ; it has 
solved many great problems that seemed insoluble a 
hundred years ago ; it has opened out to us new prov- 
inces of learning, the very existence of which was un- 
suspected at the beginning of the century. Above all, 
it has put clearly before our eyes the lofty aim of mon- 
istic cosmology, and has pointed out the path which 
alone will lead us towards it the way of the exact em- 
pirical investigation of facts, and of the critical genetic 
study of their causes. The great abstract law of me- 
chanical causality, of which our cosmological law 
the law of substance is but another and a concrete 
expression, now rules the entire universe, as it does the 
mind of man; it is the steady, immovable pole-star, 
whose clear light falls on our path through the dark 
labyrinth of the countless separate phenomena. To 
see the truth of this more clearly, let us cast a brief 
glance at the astonishing progress which the chief 
branches of science have made in this remarkable 


The study of the heavens is the oldest, the study of 
man the youngest, of the sciences. With regard to 
himself and the character of his being man only ob- 
tained a clear knowledge in the second half of the pres- 
ent century ; with regard to the starry heavens, the mo- 
tions of the planets, and so on, he had acquired aston- 
ishing information forty-five hundred years ago. The 
ancient Chinese, Hindoos, Egyptians, and Chaldaeans 
in the distant East knew more of the science of the 
spheres than the majority of educated Christians did in 
the West four thousand years after them. An eclipse 
of the sun was astronomically observed in China in the 



year 2697 B.C., and the plane of the ecliptic was deter- 
mined by means of a gnome eleven hundred years B.C., 
while Christ himself had no knowledge whatever of as- 
tronomy indeed, he looked out upon heaven and earth, 
nature and man, from the very narrowest geocentric 
and anthropocentric point of view. The greatest ad- 
vance of astronomy is generally, and rightly, said to be 
the founding of the heliocentric system of Copernicus, 
whose famous work, De Revolutionibus Orbium Celes- 
tium, of itself caused a profound revolution in the minds 
of thoughtful men. In overthrowing the Ptolemaic 
system, he destroyed the foundation of the Christian 
theory, which regarded the earth as the centre of the 
universe and man as the godlike ruler of the earth. 
It was natural, therefore, that the Christian clergy, 
with the pope at its head, should enter upon a fierce 
struggle with the invaluable discovery of Copernicus. 
Yet it soon cleared a path for itself, when Kepler and 
Galileo grounded on it their true " mechanics of the 
heavens," and Newton gave it a solid foundation by 
his theory of gravitation (1686). 

A further great advance, comprehending the entire 
universe, was the application of the idea of evolution 
to astronomy. It was done by the youthful Kant in 
!755 i i n his famous general natural history and theory 
of the heavens he undertook the discussion, not only 
of the " constitution," but also of the " mechanical ori- 
gin " of the whole world-structure on Newtonian prin- 
ciples. The splendid Systeme du Monde of Laplace, 
who had independently come to the same conclusions 
as Kant on the world-problem, gave so firm a basis to 
this new Mecanique Celeste in 1796 that it looked as 
if nothing entirely new of equal importance was left 
to be discovered in the nineteenth century. Yet here 



again it had the honor of opening out entirely new 
paths and infinitely enlarging our outlook on the uni- 
verse. The invention of photography and photome- 
try, and especially of spectral analysis (in 1860 by 
Bunsen and Kirchoff), introduced physics and chem- 
istry into astronomy and led to cosmological conclu- 
sions of the utmost importance. It was now made 
perfectly clear that matter is the same throughout the 
universe, and that its physical and chemical properties 
in the most distant stars do not differ from those of the 
earth under our feet. 

The monistic conviction, which we thus arrived at, 
of the physical and chemical unity of the entire cosmos 
is certainly one of the most valuable general truths 
which we owe to astrophysics, the new branch of as- 
tronomy which is honorably associated with the name 
of Friedrich Zollner. Not less important is the clear 
knowledge we have obtained that the same laws of 
mechanical development that we have on the earth rule 
throughout the infinite universe. A vast, all-embrac- 
ing metamorphosis goes on continuously in all parts of 
the universe, just as it is found in the geological his- 
tory of the earth ; it can be traced in the evolution of 
its living inhabitants as surely as in the history of peo- 
ples or in the life of each human individual. In one 
part of space we perceive, with the aid of our best tele- 
scopes, vast nebulae of glowing, infinitely attenuated 
gas ; we see in them the embryos of heavenly bodies, 
billions of miles away, in the first stage of their devel- 
opment. In some of these " stellar embryos " the 
chemical elements do not seem to be differentiated yet, 
but still buried in the homogeneous primitive matter 
(prothyl) at an enormous temperature (calculated to run 
into millions of degrees) ; it is possible that the origi- 



nal basic " substance " (vide p. 229) is not yet divided 
into ponderable and imponderable matter. In other 
parts of space we find stars that have cooled down into 
glowing fluid, and yet others that are cold and rigid ; 
we can tell their stage of evolution approximately by 
their color. We find stars that are surrounded with 
rings and moons like Saturn ; and we recognize in the 
luminous ring of the nebula the embryo of a new moon, 
which has detached itself from the mother-planet, just 
as the planet was released from the sun. 

Many of the stars, the light of which has taken thou- 
sands of years to reach us, are certainly suns like our 
own mother-sun, and are girt about with planets and 
moons, just as in our own solar system. We are justified 
in supposing that thousands of these planets are in a 
similar stage of development to that of our earth that 
is, they have arrived at a period when the temperature 
at the surface lies between the freezing and boiling 
point of water, and so permits the existence of water 
in its liquid condition. That makes it possible that 
carbon has entered into the same complex combinations 
on those planets as it has done on our earth, and that 
from its nitrogenous compounds protoplasm has been 
evolved that wonderful substance which alone, as far 
as our knowledge goes, is the possessor of organic life. 
The monera (for instance, chromacea and bacteria), 
which consist only of this primitive protoplasm, and 
which arise by spontaneous generation from these in- 
organic nitrocarbonates, may thus have entered upon 
the same course of evolution on many other planets as 
on our own; first of all, living cells of the simplest 
character would be formed from their homogeneous 
protoplasmic body by the separation of an inner nu- 
cleus from the outer cell body (cytostoma). Further, 



the analogy that we find in the life of all cells whether 
plasmodomous plant-cells or plasmophagous animal- 
cells justifies the inference that the further course of 
organic evolution on these other planets has been 
analogous to that of our own earth always, of course, 
given the same limits of temperature which permit water 
in a liquid form. In the glowing liquid bodies of the 
stars, where water can only exist in the form of steam, 
and on the cold extinct suns, where it can only be in the 
shape of ice, such organic life as we know is impossible. 

The similarity of phylogeny, or the analogy of or- 
ganic evolution, which we may thus assume in many 
stars which are at the same stage of biogenetic devel- 
opment, naturally opens out a wide field of brilliant 
speculation to the constructive imagination. A favor- 
ite subject for such speculation has long been the ques- 
tion whether there are men, or living beings like our- 
selves, perhaps much more highly developed, in other 
planets? Among the many works which have sought 
to answer the question, those of Camille Flammarion, 
the Parisian astronomer, have recently been extremely 
popular; they are equally distinguished by exuberant 
imagination and brilliant style, and by a deplorable 
lack of critical judgment and biological knowledge. 
We may condense in the following thesis the present 
condition of our knowledge on the subject : 

I. It is very probable that a similar biogenetic proc- 
ess to that of our own earth is taking place on some of 
the other planets of our solar system (Mars and Venus), 
and on many planets of other solar systems ; first sim- 
ple monera are formed by spontaneous generation, and 
from these arise unicellular protists (first plasmodom- 
ous primitive plants, and then plasmophagous primi- 
tive animals). 



II. It is very probable that from these unicellular 
protists arise, in the further course of evolution, first 
social cell-communities (ccenobia), and subsequently 
tissue-forming plants and animals (metaphyta and 

III. It is also very probable that thallophyta (algae 
and fungi) were the first to appear in the plant-king- 
dom, then diaphyta (mosses and ferns), finally antho- 
phyta (gymnosperm and angiosperm flowering plants). 

IV. It is equally probable that the biogenetic proc- 
ess took a similar course in the animal kingdom 
that from the blastaeads (catallacta) first gastraeads 
were formed, and from these lower animal forms (cce- 
lenteria) higher organisms (coelomaria) were afterwards 

V. On the other hand, it is very questionable wheth- 
er the different stems of these higher animals (and 
those of the higher plants as well) run through the 
same course of development on other planets as on our 

VI. In particular, it is wholly uncertain whether 
there are vertebrates on other planets, and whether, 
in the course of their phyletic development, taking 
millions of years, mammals are formed as on earth, 
reaching their highest point in the formation of man ; 
in such an event, millions of changes would have to 
be just the same in both cases. 

VII. It is much more probable, on the contrary, that 
other planets have produced other types of the higher 
plants and animals, which are unknown on our earth ; 
perhaps from some higher animal stem, which is su- 
perior to the vertebrate in formation, higher beings 
have arisen who far transcend us earthly men in 


VIII. The possibility of our ever entering into di- 
rect communication with such inhabitants of other 
planets seems to be excluded by the immense distance 
of our earth from the other heavenly bodies, and the 
absence of the requisite atmosphere in the intervening 
space, which contains only ether. 

But while many of the stars are probably in a sim- 
ilar stage of biogenetic development to that of our earth 
(for the last one hundred million years at least), others 
have advanced far beyond this stage, and, in their plan- 
etary old age, are hastening towards their end the 
same end that inevitably awaits our own globe. The 
radiation of heat into space gradually lowers the tem- 
perature until all the water is turned into ice; that 
is the end of all organic life. The substance of the 
rotating mass contracts more and more ; the rapidity 
of its motion gradually falls off. The orbits of the 
planets and of their moons grow narrower. At length 
the moons fall upon the planets, and the planets are 
drawn into the sun that gave them birth. The col- 
lision again produces an enormous quantity of heat. 
The pulverized mass of the colliding bodies is distrib- 
uted freely through infinite space, and the eternal 
drama of sun-birth begins afresh. 

The sublime picture which modern astrophysics 
thus unveils before the mind's eye shows us an eternal 
birth and death of countless heavenly bodies, a peri- 
odic change from one to the other of the different cos- 
mogenetic conditions, which we observe side by side 
in the universe. While the embryo of a new world is 
being formed from a nebula in one corner of the vast 
stage of the universe, another has already condensed 
into a rotating sphere of liquid fire in some far distant 
spot ; a third has already cast off rings at its equator, 



which round themselves into planets ; a fourth has be- 
come a vast sun whose planets have formed a second- 
ary retinue of moons, and so on. And between them 
are floating about in space myriads of smaller bodies, 
meteorites, or shooting-stars, which cross and recross 
the paths of the planets apparently like lawless vaga- 
bonds, and of which a great number fall onto the plan- 
ets every day. Thus there is a continuous but slow 
change in the velocities and the orbits of the revolving 
spheres. The frozen moons fall onto the planets, 
the planets onto their suns. Two distant suns, per- 
haps already stark and cold, rush together with in- 
conceivable force and melt away into nebulous clouds. 
And such prodigious heat is generated by the collision 
that the nebula is once more raised to incandescence, 
and the old drama begins again. Yet in this " per- 
petual motion " the infinite substance of the universe, 
the sum total of its matter and energy, remains eter- 
nally unchanged, and we have an eternal repetition 
in infinite time of the periodic dance of the worlds, the 
metamorphosis of the cosmos that ever returns to its 
starting-point. Over all rules the law of substance. 


The earth and its origin were much later than the 
heavens in becoming the object of scientific investiga- 
tion. The numerous ancient and modern cosmogonies 
do, indeed, profess to give us as good an insight into 
the origin of the earth as into that of the heavens ; but 
the mythological raiment, in which all alike are clothed, 
betrays their origin in poetic fancy. Among the count- 
less legends of creation which we find in the history of 
religions and of thought there is one that soon took 



precedence of all the rest the Mosaic story of creation 
as told in the first book of the Hexateuch. It did not 
exist in its present form until long after the death of 
Moses (probably not until eight hundred years after- 
wards) ; but its sources are much older, and are to be 
found for the most part in Assyrian, Babylonian, and 
Hindoo legends. This Hebrew legend of creation ob- 
tained its great influence through its adoption into the 
Christian faith and its consecration as the " Word of 
God." Greek philosophers had already, five hundred 
years before Christ, explained the natural origin of the 
earth in the same way as that of other cosmic bodies. 
Xenophanes of Colophon had even recognized the true 
character of the fossils which were afterwards to prove 
of such moment ; the great painter, Leonardo da Vinci, 
of the fifteenth century, also explained the fossils as 
the petrified remains of animals which had lived in 
earlier periods of the earth's history. But the author- 
ity of the Bible, especially the myth of the deluge, pre- 
vented any further progress in this direction, and in- 
sured the triumph of the Mosaic legend until about the 
middle of the last century. It survives even at the 
present day among orthodox theologians. However, 
in the second half of the eighteenth century, scientific 
inquiry into the structure of the crust of the earth set 
to work independently of the Mosaic story, and it soon 
led to certain conclusions as to the origin of the earth. 
The founder of geology, Werner of Freiberg, thought 
that all the rocks were formed in water, while Voigt 
and Hutton (1788) rightly contended that only the 
stratified, fossil-bearing rocks had had an aquatic ori- 
gin, and that the Vulcanic or Plutonic mountain ranges 
had been formed by the cooling down of molten matter. 
The heated conflict of these " Neptunian " and " Plu- 


tonic " schools was still going on during the first three 
decades of the present century ; it was only settled when 
Karl Hoff (1822) established the principle of "actual- 
ism," and Sir Charles Lyell applied it with signal suc- 
cess to the entire natural evolution of the earth. The 
Principles of Geology of Lyell (1830) secured the full 
recognition of the supremely important theory of con- 
tinuity in the formation of the earth's crust, as opposed 
to the catastrophic theory of Cuvier.* Palaeontology, 
which had been founded by Cuvier's work on fossil 
bones (1812), was of the greatest service to geology; 
by the middle of the present century it had advanced 
so far that the chief periods in the history of the earth 
and its inhabitants could be established. The com- 
paratively thin crust of the earth was now recognized 
with certainty to be the hard surface formed by the 
cooling of an incandescent fluid planet, which still con- 
tinues its slow, unbroken course of refrigeration and 
condensation. The crumpling of the stiffened -crust, 
" the reaction of the molten fiery contents on the cool 
surface," and especially the unceasing geological ac- 
tion of water, are the natural causes which are daily 
at work in the secular formation of the crust of the 
earth and its mountains. 

To the brilliant progress of modern geology we owe 
three extremely important results of general import. In 
the first place, it has excluded from the story of the 
earth all questions of miracle, all questions of super- 
natural agencies, in the building of the mountains and 
the shaping of the continents. In the second place, 
our idea of the length of the vast period of time which 
had been absorbed in their formation has been consid- 

*Cf. The Natural History of Creation, chaps, iii., vi., xv., and 



erably enlarged. We now know that the huge moun- 
tains of the palaeozoic, mesozoic, and cenozoic forma- 
tions have taken, not thousands, but millions of years 
in their growth. In the third place, we now know that 
all the countless fossils that are found in those forma- 
tions are not " sports of nature/' as was believed one 
hundred and fifty years ago, but the petrified remains 
of organisms that lived in earlier periods of the earth's 
history, and arose by gradual transformation from a 
long series of ancestors. 


The many important discoveries which these funda- 
mental sciences have made during the nineteenth cen- 
tury are so well known, and their practical application 
in every branch of modern life is so obvious, that we 
need not discuss them in detail here. In particular, 
the application of steam and electricity has given to 
our nineteenth century its characteristic " machinist- 
stamp." But the colossal progress of inorganic and 
organic chemistry is not less important. All branches 
of modern civilization medicine and technology, in- 
dustry and agriculture, mining and forestry, land and 
water transport have been so much improved in the 
course of the century, especially in the second half, 
that our ancestors of the eighteenth century would find 
themselves in a new world, could they return. But 
more valuable and important still is the great theoreti- 
cal expansion of our knowledge of nature, which we 
owe to the establishment of the law of substance. Once 
Lavoisier (1789) had established the law of the persist- 
ence of matter, and Dalton (1808) had founded his new 
atomic theory with its assistance, a way was open to 



modern chemistry along which it has advanced with a 
rapidity and success beyond all anticipation. The 
same must be said of physics in respect of the law of 
the conservation of energy. Its discovery by Robert 
Mayer (1842) and Hermann Helmholtz (1847) inaugu- 
rated for this science also a new epoch of the most fruit- 
ful development; for it put physics in a position to 
grasp the universal unity of the forces of nature and 
the eternal play of natural processes, in which one 
force may be converted into another at any moment. 


The great discoveries which astronomy and geology 
have made during the nineteenth century, and which 
are of extreme importance to our whole system, are, 
nevertheless, far surpassed by those of biology. In- 
deed, we may say that the greater part of the many 
branches which this comprehensive science of organic 
life has recently produced have seen the light in the 
course of the present century. As we saw in the first 
section, during the century all branches of anatomy 
and physiology, botany and zoology, ontogeny and phy- 
logeny, have been so marvellously enriched by count- 
less discoveries that the present condition of biological 
science is immeasurably superior to its condition a 
hundred years ago. That applies first of all quanti- 
tatively to the colossal growth of our positive informa- 
tion in all those provinces and their several parts. But 
it applies with even greater force qualitatively to the 
deepening of our comprehension of biological phenom- 
ena, and our knowledge of their efficient causes. In 
this Charles Darwin (1859) takes the palm of victory ; 
by his theory of selection he has solved the great prob- 



lem of " organic creation," of the natural origin of the 
countless forms of life by gradual transformation. 
It is true that Lamarck had recognized fifty years 
earlier that the mode of this transformation lay in the 
reciprocal action of heredity and adaptation. How- 
ever, Lamarck was hampered by his lack of the prin- 
ciple of selection, and of that deeper insight into the true 
nature of organization which was only rendered possi- 
ble after the founding of the theory of evolution and 
the cellular theory. When we collated the results of 
these and other disciplines, and found the key to their 
harmonious interpretation in the ancestral development 
of living beings, we succeeded in establishing the mon- 
istic biology, the principles of which I have endeavored 
to lay down securely in my General Morphology. 


In a certain sense, the true science of man, rational 
anthropology, takes precedence of every other science. 
The saying of the ancient sage, "Man, know thyself," 
and that other famous maxim, "Man is the measure 
of all things," have been accepted and applied from all 
time. And yet this science taking it in its widest sense 
has languished longer than all other sciences in the 
fetters of tradition and superstition. We saw in the 
first section how slowly and how late the science of 
the human organism was developed. One of its chief 
branches embryology was not firmly established 
until 1828 (by Baer), and another, of equal importance 
the cellular theory until 1838 (by Schwann). And 
it was even later still when the answer was given to the 
"question of all questions," the great riddle of the 
origin of man. Although Lamarck had pointed out 



the only path to a correct solution of it in 1809, and 
had affirmed the descent of man from the ape, it fell to 
Darwin to establish the affirmation securely fifty years 
afterwards, and to Huxley to collect the most important 
proofs of it in 1863, in his Place of Man in Nature. 
I have myself made the first attempt, in my Anthro- 
pogeny (1874), to present in their historical connection 
the entire series of ancestors through which our race 
has been slowly evolved from the animal kingdom in 
the course of many millions of years. 


number of world-riddles has been continually 
diminishing in the course of the nineteenth century 
through the aforesaid progress of a true knowledge of 
nature. Only one comprehensive riddle of the universe 
now remains the problem of substance. What is 
the real character of this mighty world-wonder that 
the realistic scientist calls Nature or the Universe, the 
idealist philosopher calls Substance or the Cosmos, 
the pious believer calls Creator or God? Can we affirm 
to-day that the marvellous progress of modern cosmol- 
ogy has solved this " problem of substance/' or at least 
that it has brought us nearer to the solution? 

The answer to this final question naturally varies con- 
siderably according to the stand-point of the philosophic 
inquirer and his empirical acquaintance with the real 
world. We grant at once that the innermost character 
of nature is just as little understood by us as it was by 
Anaximander and Empedocles twenty-four hundred 
years ago, by Spinoza and Newton two hundred years 
ago, and by Kant and Goethe one hundred years ago. 
We must even grant that this essence of substance be- 
comes more mysterious and enigmatic the deeper we 
penetrate into the knowledge of its attributes, matter 
and energy, and the more thoroughly we study its 
countless phenomenal forms and their evolution. We 
do not know the " thing in itself " that lies behind these 
knowable phenomena. But why trouble about this 



enigmatic "thing in itself" when we have no means 
of investigating it, when we do not even clearly know 
whether it exists or not? Let us, then, leave the fruit- 
less brooding over this ideal phantom to the "pure 
metaphysician/' and let us instead, as "real physi- 
cists," rejoice in the immense progress which has been 
actually made by our monistic philosophy of nature. 

Towering above all the achievements and discov- 
eries of the century we have the great, comprehensive 
"law of substance," the fundamental law of the con- 
stancy of matter and frce. The fact that substance 
is everywhere subject to eternal movement and trans- 
formation gives it the character also of the universal 
law of evolution. As this supreme law has been firm- 
ly established, and all others are subordinate to it, we 
arrive at a conviction of the universal unity of nature 
and the eternal validity of its laws. From the gloomy 
problem of substance we have evolved the clear law 
of substance. The monism of the cosmos which we 
establish thereon proclaims the absolute dominion of 
" the great eternal iron laws " throughout the universe. 
It thus shatters, at the same time, the three central 
dogmas of the dualistic philosophy the personality 
of God, the immortality of the soul, and the freedom 
of the will. 

Many of us certainly view with sharp regret, or even 
with a profound sorrow, the death of the gods that were 
so much to our parents and ancestors. We must con- 
sole ourselves in the words of the poet : 

* The times are changed, old systems fall, 
And new life o'er their ruins dawns." 

The older view of idealistic dualism is breaking up 
with all its mystic and anthropistic dogmas ; but upon 
*> 381 


the vast field of ruins rises, majestic and brilliant, the 
new sun of our realistic monism, which reveals to us 
the wonderful temple of nature in all its beauty. In 
the sincere cult of " the true, the good, and the beauti- 
ful," which is the heart of our new monistic religion, 
we find ample compensation for the anthropistic ideals 
of "God, freedom, and immortality" which we have 

Throughout this discussion of the riddles of the uni- 
verse I have clearly defined my consistent monistic 
position and its opposition to the still prevalent dual- 
istic theory. In this I am supported by the agreement 
of nearly all modern scientists who have the courage 
to accept a rounded philosophical system. I must not, 
however, take leave of my readers without pointing 
out in a conciliatory way that this strenuous opposition 
may be toned down to a certain degree on clear and 
logical reflection may, indeed, even be converted 
into a friendly harmony. In a thoroughly logical 
mind, applying the highest principles with equal force 
in the entire field of the cosmos in both organic and 
inorganic nature the antithetical positions of theism 
and pantheism, vitalism and mechanism, approach 
until they touch each other. Unfortunately, consec- 
utive thought is a rare phenomenon in nature. The 
great majority of philosophers are content to grasp 
with the right hand the pure knowledge that is built 
on experience, but they will not part with the mystic 
faith based on revelation, to which they cling with the 
left. The best type of this contradictory dualism is 
the conflict of pure and practical reason in the critical 
philosophy of the most famous of modern thinkers, 
Immanuel Kant. 

On the other hand, the number is always small of 



the thinkers who will boldly reject dualism and em- 
brace pure monism. That is equally true of consist- 
ent idealists and theists, and of logical realists and 
pantheists. However, the reconciliation of these ap- 
parent antitheses, and, consequently, the advance 
towards the solution of the fundamental riddle of the 
universe, is brought nearer to us every year in the ever- 
increasing growth of our knowledge of nature. We 
may, therefore, express a hope that the approaching 
twentieth century will complete the task of resolving 
the antitheses, and, by the construction of a system 
of pure monism, spread far and wide the long-desired 
unity of world-conception. Germany's greatest think- 
er and poet, whose one hundred and fiftieth anniver- 
sary will soon be upon us Wolfgang Goethe gave 
this " philosophy of unity" a perfect poetic expression, 
at the very beginning of the century, in his immortal 
poems, Faust, Prometheus, and God and the World : 

" By eternal laws 
Of iron ruled, 
Must all fulfil 
The cycle of 
Their destiny/ 


Abiogenesis, 257, 369. 
Abortive organs, 264. 
Accidents, 216. 
Acrania, 1 66. 
Action at a distance, 217. 
Actualism, 249. 
^sthesis, 225. 
Affinity, 224. 
Altruism, 350. 
Amphibia, 167. 
Amphimixis, 141. 
Ampitheism, 278. 
Ananke, 272. 
Anatomy, 22, etc. 

comparative, 24. 
Anaximander, 289, 379. 
Anthropism, n. 
Anthropistic illusion, 14, etc. 

world-theory, 13. 
Anthropocentric dogma, II, etc. 
Anthropogeny, 83. 
Anthropolatric dogma, 12. 
Anthropomorpha, 36. 
Anthropomorphic dogma, 12. 
Apes, 36, 37, 167. 

anthropoid, 37. 
Archaeus, 43. 
Archigony, 257. 
Aristotle, 23, 268. 
Association, centres of, 183. 

of ideas, 121. 

of presentations, 121, 122. 
Astronomy, progress of, 366. 
Astrophysics, 368. 
Atavism, 142. 
Athanatism, 189. 

Athanatistic illusions, 205. 

Atheism, 290. 

Atheistic science, 260. 

Atom, the, 222. 

Atomism, 223. 

Atomistic consciousness, 187. 

Attributes of ether, 227. 

of substance, 216. 
Augustine of Hippo, 130. 
Auricular confession, 319, 359. 
Autogony, 257. 

Baer (Carl Ernst), 57. 
Bastian (Adolf), 103. 
Beginning of the world, 240, 


Bible, the, 282, 362. 
Biogenesis, 257. 
Biogenetic law, 81, 143. 
Bismarck, 334. 
Blastoderm, 150, 155. 
Blastosphere, 153. 
Blastula, 153. 

Bruno (Giordano), 290, 317. 
Buchner (Ludwig), 93. 
Buddhism, 326, 355. 

Calvin, 130. 
Canonical gospels, 312. 
Carbon as creator, 256. 

theory, 257. 
Catarrhinae, 35. 
Catastrophic theory, 74. 
Categorical imperative, 350. 
Causes, efficient, 258. 

final, 258. 


Celibacy, 358. 
Cell-love, 137. 

community, soul of the, 155. 

soul, 151. 

state, 157. 
Cellular pathology, 50. 

physiology, 48. 

psychology, 153, 177. 

theory, 26. 
Cenobitic soul, 155. 
Cenogenesis, 82. 

of the psyche, 144. 
Chance, 274. 
Chemicotropism, 64, 136. 
Chordula, 64. 
Chorion, 68. 
Christ, father of, 327. 
Christian art, 339. 

civilization, 356. 

contempt of the body, 354. 
animals, 355. 
nature, 355. 
self, 353- 
the family, 357. 
woman, 358. 

ethics, 352. 
Christianity, 347. 
Church and school, 362. 

state, 361. 
Cnidaria, 161. 
Conception, 64. 

Concubinage of the clergy, 358. 
Confession of faith, 302. 
Consciousness, 170. 

animal, 176. 

atomistic, 178. 

biological, 176. 

cellular, 177. 

development of, 185. 

dualistic, 182. 

human, 173. 

monistic, 182. 

neurological, 174. 

ontogeny of, 186. 

pathology of, 182. 

physiological, 1 80. 

transcendental, 1 80. 
Constancy of energy, 212, 231. 

matter, 212. 
Constantine the Great, 316. 

Constellations of substance, 218. 
Conventional lies, 323. 
Copernicus, 24, 320, 367. 
Cosmic immortality, 191. 
Cosmogonies, 234. 
Cosmological dualism, 257. 

creationism, 235. 

law, 211. 

perspective, 14. 
Cosmos, the, 229. 
Creation, 73, 79, 234. 

cosmological, 235. 

dualistic, 236. 

heptameral, 237 

individual, 237. 

myths of, 236. 

periodic, 237. 

trialistic, 237. 
Cultur-kampf, 334. 
Cuvier, 74. 
Cyclostomata, 167. 
Cynopitheci, 46. 
Cytology, 26, etc. 
Cytopsyche, 151. 
Cytula, 64. 

Darwin (Charles), 78, etc. 
Decidua, 69. 
Deduction, 16. 
Demonism, 276. 
Descartes, 99, 355. 
Descent of the ape, 85, etc. 

of man, 87. 

theory of, 77. 
Design, 264, 266. 

in nature, 260. 

in organisms, 266. 

in selection, 261. 
Destruction of heavenly bodie& 


Determimsts, 130. 
Diaphragm, 31. 
Division of labor in matte*, ^29 
Draper, 309, 333. 
Dualism, 20, etc. 
Du Bois-Reymond, 15 f 80, 235- 
Du Prel (Carl), 305. 
Duty, feeling of, 350 
Dynamodes, 216. 
Dysteleology, 260. 



Echinodermata, 62. 
Ectoderm, 160. 

sense-cells in the, 293. 
Egoism, 350. 
Elements, chemical, 222. 

system of the, 222. 
Embryo, human, 64. 
Embryology, 54. 
Embryonic psychogeny, 144. 

sleep, 146. 

Empedocles, 23, 224. 
Encyclica (of Pius IX.), 323. 
End of the world, 247. 
Energy, kinetic, 231. 

potential, 231. 

principle of, 230. 

specific, 294. 
Entelecheia, 268. 
Entoderm, 160. 
Entropy of the universe, 247. 
Epigenesis, 56, 133. 
Ergonomy of matter, 229. 
Eternity of the world, 242. 
Ether, 225. 
Etheric souls, 199. 
Ethics, fundamental law of, 350. 
Evolution, theory of, 54, 239, 


chief element in, 267. 
Experience, 16. 
Extra-mundane God, 288. 

Faith, confession of, 303. 

of our fathers, 304. 
Family, the, and Christianity, 


Fate, 272. 
Fechner, 97, etc. 
Fecundation, 63. 
Fetishism, 276. 
Feuerbach (Ludwig), 295. 
Flechsig, 183. 
Foetal membranes, 66. 
Folk-psychology, 103. 
Forces, conversion of, 231. 
Frederick the Great, 194, 315. 

Galen, 23, 40. 
Gaseous souls, 199. 
vertebrates, 288. 

Gastraea, 1 60. 

theory of the, 60. 
Gastraeads, 159. 
Gastrula, 61. 
Gegenbaur, 25, 30. 
Generation, theory of, 55. 
Genus, 73. 
Geology, periods of, 270. 

progress of, 373. 
Germinal disk, 57. 
Gills, 65. 
God, 275. 

the father, 277. 

the son, 277, 328. 
Goethe, 20, etc. 
Goethe's monism, 331. 
Golden Rule, the, 351. 
Gospels, 312. 

Gravitation, theory of, 217. 
Gut-layer, 159. 

Haller, 42. 

Harvey, 42. 

Helmholtz (Hermann), 213, 230. 

Heredity, psychic, 138. 

Hertz (Heinrich), 225. 

Hippocrates, 23. 

Histology, 26. 

Histopsyche, 156. 

Hoff (Carl), 250. 

Holbach (Paul), 193. 

Holy Ghost, 277, 326. 

Humboldt (Alexander), 343. 

Hydra, 161. 

Hylozoism, 289. 

Hypothesis, 299. 

latrochemicists, 45. 
latromechanicists, 45. 
Ideal of beauty, 338. 

of truth, 337. 

of virtue, 339. 
Ignorabimus, 180. 
Immaculate conception, 326. 
Immaterial substance, 221. 
Immortality of animals, 201. 

of the human soul, 188. 

of unicellular organisms, 

personal, 192. 



Imperfection of nature, 264. 
Imponderable matter, 225. 
Impregnation, 64. 
Indeterminists, 130. 
Induction, 16. 
Indulgences, 359. 
Infallibility of the pope, 324. 
Instinct, 105, 123. 
Intellect, 125, etc. 
Intramundane God, 288. 
Introspective psychology, 95. 
Islam, 284. 

Janssen (Johannes), 316. 
Jehovah, 283. 
Journeys on foot, 364. 

Kant, 258, etc. 

Kant's metamorphosis, 92, etc. 

Kinetic energy, 231. 

theory of substance, 216. 
K6lliker, 26, 48. 

Lamarck, 76, etc. 
Lamettrie, 194. 
Landscape-painting, 343. 
Language, 126. 

study of, 363. 
Last judgment, 209. 
Lavoisier, 212. 
Leap of the gospels, miraculous, 


Leydig, 27. 
Life, definition of, 39. 
Limits of our knowledge, 182. 
Love, 357- 

of animals, 355. 

of neighbor, 350. 

of self, 350. 
Lucretius Carus, 290. 
Lunarism, 281. 
Luther, 320. 
Lyell, 77, 250. 

Madonna, cult of the, 284, 327. 
Malphigi, 54. 
Mammals, 30, etc. 
Mammary glands, 31. 
Man, ancestors of, 82. 
Marsupials, 32, 86. 

Mass, 222. 
Materialism, 20. 
Mayer (Robert), 213, 377. 
Mechanical causality, 366. 

explanation, 259. 

theory of heat, 247. 
Mechanicism, 259. 
Mediterranean religions, the,282. 
Memory, cellular, 120. 

conscious, 121. 

histionic, 121 

unconscious, 121. 
Mephistppheles, 279. 
Metabolism, 232. 
Metamorphoses of the cosmos, 

of philosophers, 92. 
Metaphyta, 156. 
Metasitism, 153. 
Metazoa, 60, 157. 
Middle Ages, 315, 358. 
Mixotheism, 286. 
Mohammedanism, 284. 
Mohr (Friedrich), 213. 
Monera, 257, 369. 
Monism, 20, and passim. 

of energy, 254. 

of Spinoza, 331. 

of the cosmos, 255. 
Monistic anthropogeny, 252. 

art, 341. 

biogeny, 251. 

churches, 345. 

cosmology, 368. 

ethics, 347. 

geogeny, 248. 
Monotheism, 279. 
Monotrema, 32. 
Moon- worship, 281. 
Moral order of the universe, 269 
Morula, 155. 
Mosaism, 283. 

Muller (Johannes), 25, 45, 262. 
Mythology of the soul, 135. 

Natural religion, 344. 
Navel-cord, 69. 
Neo-kantians, 349. 
Neo vitalism, 264. 
Neptunian geology, 375. 



Ncuro-muscular cells, 114. 
Neuroplasm, 91, 109. 
Neuropsyche, 162. 
Nomocracy, 9. 

Ontogenetic psychology, 103. 
Ontological creationisra, 235. 

methods, 249. 
Orbits of the heavenly bodies, 

Origin of movement, 15, 241. 

of feeling, 15, 241. 
Ovary, 63. 

Palingenesis, 82. 

of the psyche, 143. 
Pandera (the father of Christ), 


Pantheism, 288. 
Papacy, 314. 
Papal ethics, 359. 
Papiomorpha, 37. 
Paul, 313, 357. 

epistles of, 312. 
Paulinism, 313. 
Pedicle of the allantois, 69. 
Perpetual motion, 245. 
Persistence of force, 212, 231. 

of matter, 212. 
Phroneta, 293. 
Phylogeny, 71, 8l. 

of the apes, 51. 

systematic, 8l. 
Physiology, 39. 
Phytopsyche, 157. 
Pithecanthropus, 87. 
Pithecoid theory, 82, etc. 
Pithecometra-thesis, 69, 85. 
Placenta, 32, 68. 
Placentals, 32, 86. 
Plasmodoma, 153. 
Plasmogony, 257. 
Plasmophaga, 154. 
Plato, 99, 197. 
Plato's theory of ideas, 269. 
Platodaria, 1 60. 
Platodes, 160. 
Platyrrhinae, 35. 
Pneuma zoticon, 40. 
Polytheism, 276. 

Ponderable matter, 222. 
Preformation theory, 54. 
Primaria, 33. 
Primates, 33, 86. 
Primitive Christianity, 311. 

gut, 6l, 161. 
Prodynamis, 216, 
Progaster, 161. 
Proplacentals, 85. 
Prosimiae, 34. 
Prostoma, 161. 
Prothyl, 223. 
Protoplasm, 90. 
Protozoa, 60. 
Pro vertebrae, 166. 
Pseudo-Christianity, 321. 
Psychade theory, 178. 
Psyche, 88. 
Psychogeny, 135. 

phyletic, 149. 

post-embryonic, 146. 
Psychology, 88 et seqq. 

ontogenetic, 104. 

phylogenetic, 104. 
Psychomonism, 226. 
Psychophysics, 97. 
Psychoplasm, 91, 1 10. 
Pupa, sleep of the, 146. 
Pyknosis, 218. 

Pyknotic theory of substance, 

Reason, 17, 125. 
Reflex action, 112. 

arches, 114. 
Reformation, the, 319. 
Religion a private concern, 361. 
Remak, 58. 
Revelation, 306. 
Reversion, 142. 
Romance of the Virgin Mary, 


Romanes, 106. 
Rudimentary organs, 264. 

Saints, 284. 

Scale of emotion, 127. 

of memory, 1 20. 

of movement, ill. 

of presentation, 118. 



Scale of reason, 122. 

of reflex action, 113. 

of will, 127. 
Scatulation theory, 55. 
Schleiden, 26, 47. 
School, and Church, 361. 

and State, 362. 

reform of the, 363. 
Schwann, 26, 47. 
Selachii, 166. 
Selection, theory of, 79. 
Self-consciousness, 171. 
Sense-knowledge, 297. 

organs, 293. 

Senses, philosophy of the, 295. 
Sentiment, 17, etc., 331. 
Siebold, 27. 
Simiae, 34. 
Social duties, 351. 

instincts, 350. 
Solar systems, 241, 369. 
Solarism, 280. 
Soul, 88 et seqq. 

apparatus of the, 162. 

blending of the, 141. 

creation of the, 135. 

division of the, 135. 

etheric, 199. 

gaseous, 199. 

histionic, 157. 

history of the, 167. 

hydra, 161. 

life of the, 90. 

liquid, 200. 

mammal, 167. 

nerve, 162. 

origin of the, 135. 

of the plant, 157. 

personal, 162. 

solid, 201. 

substance of the, 198. 

transmigration of the, 135. 
Sources of knowledge, 293. 
Space and time, 244. 

infinity of, 242. 

reality of. 244. 
Species, 73. 
Spectral analysis, 241. 
Spermarium, 63, 
Spermatozoa, 58. 

Spinal cord, 165. 
Spinoza, 21, 215, 290. 
Spirit world, 221. 
Spirit-rapping, 305. 
Spiritism, 304. 
Spiritualism, 20. 
Sponge, soul of the, 161. 
Stem-cell, 63, 138, 151. 
Stimulated movement, 113, 116. 
Stimuli, conduction of, 158. 
Strauss (David), 309, 313. 
Struggle for life, 270. 
Substance, 215. 

law of, 211, etc. 

structure of, 229. 
Superstition, 301. 
Suss (Edward), 250. 
Syllabus, 323. 
Synodikon (of Pappus), 312. 

Table-turning, 305. 
Teleological explanation, 259. 
Teleology, 258. 
Tetrapoda, 29. 
Thanatism, 189. 

primary, 192. 

secondary, 192. 
Theism, 276. 
Theocracy, 9. 
Theory, 299. 

Thought, organs of, 126, 183, 293. 
Time and space, 244. 

reality of, 246. 
Tissue, theory of, 26. 
Tissue-forming animals, 157. 

plants, 156. 
Transformism, 76. 
Trimurti, 278. 
Trinity, dogma of the, 277. 

monistic, 336. 
Triplotheism, 277. 
Tropesis, 225. 
Tropismata, 128. 
Tunicata, 165. 
Turbellaria, 161. 

Ultramontanism, 310. 
Understanding, 125. 
Unity of natural forces, 231. 
of substance, 214. 



Universum perpetuum mobile, 
T 245. 
Uterus, 34. 

Vaticanism, 314. 
Vertebrates, 27, passim. 
Verworn (Max), 48, 116. 
Vesalius, 24. 
Vibration, theory of, 216. 
Virchow, 26, 50. 
Virchow's metamorphosis, 93. 
Vital force, 42, 262. 
Vitalism, 43, 262. 

Vivisection, 41. 
Vogt (Carl), 93. 
Vogt (J.E.), 218. 

Water-color drawing, 364. 

Weismann, 190. 

Will, liberty of the, 129. 

scale of the, 128. 
Wolff (C.F.), 56. 
Woman and Christianity, 358. 
World-consciousness, 171. 
World-riddles, number of, 15. 
Wundt (Wilhelm), 100, 171. 





Books not returned on time are subject to a fine of 50c 
per volume after the third day overdue, increasing to 
$1.00 per volume after the sixth day. Books not in de- 
mand may be renewed if application is made before expi- 
ration of loan period. 

FEB 1 7 1950 
34 DAY 


DEC J t> 1994 


3 1378 00619 7555 


Library of the 
University of California Medical School and Hospitals